Effect of Electromagnetic Interaction on Galactic Center Flare
  Components
  Recently, near-infrared GRAVITY@ESO observations at $2.2\,\mu{\rm m}$ have
announced the detection of three bright "flares" in the vicinity of the
Galactic center supermassive black hole (SMBH) that exhibited orbital motion at
a distance of about $6 - 11$ gravitational radii from an $\sim 4\times 10^6\,
M_{\odot}$ black hole. There are indications of the presence of a large-scale,
organized component of the magnetic field at the Galactic center.
Electromagnetic effects on the flare dynamics were previously not taken into
account despite the relativistic motion of a plasma in magnetic field leading
to the charge separation and nonnegligible net charge density in the plasma.
Applying various approaches, we find the net charge number density of the flare
components of the order of $10^{-3} - 10^{-4}$ cm$^{-3}$, while the particles'
total number density is of the order of $10^{6} - 10^{8}$ cm$^{-3}$. However,
even such a tiny excess of charged particles in the quasi-neutral plasma can
significantly affect the dynamics of flare components, which can then lead to
the degeneracy in the measurements of spin of the SMBH. Analyzing the dynamics
of recent flares in the case of the rapidly rotating black hole, we also
constrain the inclination angle between the magnetic field and spin axis to
$\alpha < 50^{\circ}$, as for larger angles, the motion of the hot spot is
strongly chaotic.
