Lightning Discharges Producing Beams of Relativistic Runaway Electrons Into Space

Strong electric fields associated with lightning generate brief (~1 ms) but intense Terrestrial Gamma-ray Flashes (TGFs). A few events are thought to be the signature of a relativistic electron beam escaping the atmosphere. Such an event is distinguishable from a TGF since the lightning discharge is along the geomagnetic field line from the spacecraft, rather than below. We present the first unambiguous detections of lightning along the geomagnetic field line from a satellite coincident with flashes of relativistic electrons. The associated discharges are detected by the new GLD360 VLF global lightning detection network, and by ELF/VLF and ULF radio receivers on the ground. The discharges are compared to others from the same storm, and to satellite data from the Gamma-ray Burst Monitor (GBM). Theoretical simulations are used to predict the electron-beam signature at the spacecraft, given the exact location of the lightning discharges.