First detection of the supersonic upward plasma flow structures in the early morning sector

We present the first observations of the supersonic updrafting plasma drifts in the predawn sector. Two DMSP satellites quasi-simultaneously detected two fast-speed events: one of ~385 km spatial extension and with the maximum upward velocity of 1683 m/s appeared at ~3 LT, and the other of ~1500 km large with maximum speed of 1770 m/s occurred at ~5 LT. Both supersonic structures were observed above the eastern Pacific region, separated by ~35° of longitude in space and by 45 min in time. The events occurred at the recovery phase of the geomagnetic storm of 19 February 2014, during rapid oscillations of the interplanetary magnetic field B_z and the interplanetary electric field E_y components, which increased the eastward electric field in the equatorial nighttime ionosphere and triggered the generation of plasma irregularities. The storm time penetration electric fields seem to be the principal driver of the observed supersonic events. Key Points First observations of the supersonic upward drift in the early morning sector Two supersonic events were detected quasi-simultaneously over the eastern Pacific Such events are extremely rare to occur in the early morning sector.