Introduction to TREx‐ATM V2.0: A Versatile Model of Auroral Transport and Its Effects in the Ionosphere

Abstract Auroral transport models (ATMs) play an important role in quantitative studies of optical auroras, their driving mechanisms, and their effects on the ionosphere and thermosphere. TREx‐ATM was initially developed as the support model for the Transition Region Explorer (TREx) mission, and has gained increasing applications in the community in recent years. In this paper, we introduce the recently updated TREx‐ATM V2.0. We compare the modeled emission intensities and ratios with those from two other commonly used ATMs, B3C and GLOW, and address the reasons for the moderate discrepancies among them. We articulate the recent model extension to relativistic energy ranges and the associated cross‐sections. We compare our modeled ionization rates under high‐energy electron precipitation with those computed using the existing fast calculation method and fixed branching ratios in Whole Atmosphere Community Climate Model. We also introduce the model's capability, albeit with certain limitations in the open version, to compute the profiles of ionospheric plasma density and electron temperature under auroral precipitation. Support for proton auroral ionization is also partly offered in TREx‐ATM V2.0. Finally, we describe our algorithm to invert the electron precipitation parameters, as well as the oxygen correction factor, from four‐wavelength optical data, and exemplify the inversion procedure via both numerical tests and realistic TREx data. We also demonstrate the auroral conductance data sets based on the inversion. With these updated capabilities, TREx‐ATM may offer a convenient and versatile tool for quantitative studies of auroras and magnetosphere‐ionosphere‐thermosphere‐mesosphere coupling processes.