Modulation of a SAR arc by density irregularities at plasmapause during a geomagnetic storm

The magnetospheric source region of the Stable Auroral Red (SAR) arc corresponds to the overlap of the ring current and the plasmapause. Although the density irregularities are often observed at the plasmapause, it has not been reported that the modulation of a SAR Arc by the density irregularities at plasmapause yet. This paper reports the conjugate observation of a SAR arc by ground-based imaging, magnetospheric and ionospheric satellites during the recovery phase of the geomagnetic storm on October 9, 2013. In the magnetospheric source region of the SAR arc, the Van Allen Probe B satellite observes density irregularities, in which there are EMIC waves, ring current ion distribution, and nonlinear electric field structures. The conjugate observation shows that the distribution of ring current ions in this region is capable of driving the SAR arc through the heat flux generated by Coulomb collisions. The heat flux is modulated by density irregularities, forming small-scale spatial distributions. Both Protons with energies of several keV and oxygen ions with energies of tens of keV in the ring current play a dominant role in this process. Additionally, the precipitation of low-energy electrons caused by nonlinear electric field structures superimposed on the heat flux should be attributed to the very bright SAR arc.