It is well known that the Milgrom ’ s MOND ( modified Newtonian dynamics ) explains well the mass discrepancy problem in galaxy rotation curves .
The MOND predicts a universal acceleration scale below which the Newtonian dynamics is invalid yet .
The universal acceleration scale we got from the SPARC dataset is g _ { { \dagger } } = 1.02 \times 10 ^ { -10 } ~ { } m~ { } s ^ { -2 } .
Milgrom suggested that the acceleration scale may be a fingerprint of cosmology on local dynamics and related with the Hubble constant g _ { { \dagger } } \sim cH _ { 0 } .
In this paper , we use the hemisphere comparison method with the SPARC dataset to investigate the spatial anisotropy on the acceleration scale .
We find that the hemisphere of the maximum acceleration scale is in the direction ( l,b ) = ( { 175.5 ^ { \circ } } ^ { +6 ^ { \circ } } _ { -10 ^ { \circ } } , { -6.5 ^ { \circ } } ^ { +8 ^ { \circ } } _ % { -3 ^ { \circ } } ) with g _ { { \dagger } ,max } = 1.10 \times 10 ^ { -10 } ~ { } m~ { } s ^ { -2 } , while the hemisphere of the minimum acceleration scale is in the opposite direction ( l,b ) = ( { 355.5 ^ { \circ } } ^ { +6 ^ { \circ } } _ { -10 ^ { \circ } } , { 6.5 ^ { \circ } } ^ { +3 ^ { \circ } } _ { % -8 ^ { \circ } } ) with g _ { { \dagger } ,min } = 0.76 \times 10 ^ { -10 } ~ { } m~ { } s ^ { -2 } .
The maximum anisotropy level reaches up to 0.37 \pm 0.04 .
Robust tests present that such a level of anisotropy can ’ t be reproduced by a statistically isotropic data .
In addition , we show that the spatial anisotropy on the acceleration scale has little correlation with the non-uniform distribution of the SPARC data points in sky .
We also find that the maximum anisotropy direction is close with other cosmological preferred directions , especially the direction of the “ Australia dipole ” for the fine structure constant .