  With experimental data of DIS involving transversely polarized proton, we
have calculated the 3-D charge density inside the polarized proton, which is
found to have a significant non-spherical symmetry. Then we have calculated the
property of electromagnetic field (E-M field) generated by a single
transversely polarized proton ($p^{\uparrow}$). Based on them, the E-M field
generated in small collision system $p^{\uparrow}+A$ are studied. We find that
the orientation of this E-M field has a significant dependence on the
polarization direction of the proton, and the correlator ($\Delta\gamma$ ) has
also significant dependence on the angle between reaction plane and
polarization direction. This finding provides us a new method for probing the
chiral magnetic effect (CME).
