Temporal signatures of radiation belt electron precipitation induced by lightning‐generated MR whistler waves: 2. Global signatures

Abstract

We use the methodology presented in a companion paper to calculate the temporal and spatial precipitation signatures of energetic radiation‐belt electrons due to pitch‐angle scattering by magnetospherically reflecting (MR) whistler waves generated by lightning discharges at geomagnetic source latitudes of λs = 25°, 35°, 45°, and 55°. We show precipitated energy and number fluxes, as well as average precipitated energy as a function of time and L‐shell for all four λs cases, and then extrapolate the results of the λs = 35° case in longitude to produce a time‐sequence of geographic ‘hot spots’ which are affected by the MR whistler induced electron precipitation. We then discuss the total precipitation in both hemispheres due to the various λs cases. Our major findings are that the precipitation region moves to higher L‐shells as a function of time, on short (0.1 sec, at the start of the event) and long (10 sec) timescales, corresponding to the first hop of the wave, and the MR portion of the whistler wave, respectively. There is also structure within the long‐timescale precipitation on the order of ∼1 sec, reflecting the periodic MR of the underlying whistler wave. As λs increases, an additional precipitated flux signature which is more incoherent and discontinuous, begins to form at higher L‐shells and later times, due to MR whistler wave reflections from the plasmapause. At lower L‐shells, a pronounced maximum occurs in the number flux of ∼1 keV electrons at L ∼ 2–3 due to the Landau resonance. The geographic hot spot affected by the precipitation can split into two separate regions per hemisphere, and occur simultaneously in both hemispheres so that up to four distinct precipitation hot spots can occur on the Earth at any instant, driven by a single lightning discharge. We also discuss potential sources of error, and comparison to related modeling efforts, and to observations using a either satellite‐borne instruments or ground‐based techniques.