Inferring source properties of monoenergetic electron precipitation from kappa and Maxwellian moment-voltage relationships

We present two case studies of FAST electrostatic analyzer measurements of both highly nonthermal ($\kappa \lesssim$~2.5) and weakly nonthermal/thermal monoenergetic electron precipitation at $\sim$4000~km, from which we infer the properties of the magnetospheric source distributions via comparison of experimentally determined number density--, current density--, and energy flux--voltage relationships with corresponding theoretical relationships. We also discuss the properties of the two new theoretical number density--voltage relationships that we employ. Moment uncertainties, which are calculated analytically via application of the \citet{Gershman2015} moment uncertainty framework, are used in Monte Carlo simulations to infer ranges of magnetospheric source population densities, temperatures, $\kappa$ values, and altitudes. We identify the most likely ranges of source parameters by requiring that the range of $\kappa$ values inferred from fitting experimental moment-voltage relationships correspond to the range of $\kappa$ values inferred from directly fitting observed electron distributions with two-dimensional kappa distribution functions. Observations in the first case study, which are made over $\sim$78--79$^\circ$ invariant latitude (ILAT) in the Northern Hemisphere and 4.5--5.5 magnetic local time (MLT), are consistent with a magnetospheric source population density $n_m =$~0.7--0.8~cm$^{-3}$, source temperature $T_m \approx$~70~eV, source altitude $h =$~6.4--7.7~$R_E$, and $\kappa =$~2.2--2.8. Observations in the second case study, which are made over 76--79$^\circ$~ILAT in the Southern Hemisphere and $\sim$21~MLT, are consistent with a magnetospheric source population density $n_m =$~0.07--0.09~cm$^{-3}$, source temperature $T_m \approx$~95~eV, source altitude $h \gtrsim$~6~$R_E$, and $\kappa =$~2--6

Small-scale dynamic aurora

Small-scale dynamic auroras have spatial scales of a few km or less, and temporal scales of a few seconds or less, which visualize the complex interplay among charged particles, Alfvén waves, and plasma instabilities working in the magnetosphere-ionosphere coupled regions. We summarize the observed properties of flickering auroras, vortex motions, and filamentary structures. We also summarize the development of fundamental theories, such as dispersive Alfvén waves (DAWs), plasma instabilities in the auroral acceleration region, ionospheric feedback instabilities (IFI), and the ionospheric Alfvén resonator (IAR).</p

Firefly: The Case for a Holistic Understanding of the Global Structure and Dynamics of the Sun and the Heliosphere

This white paper is on the HMCS Firefly mission concept study. Firefly focuses on the global structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the deciphering of the solar cycle, the conditions leading to the explosive activity, and the structure and dynamics of the corona as it drives the heliosphere