Models

IPWM

Ionosphere/Polar Wind Model

The ionosphere/polar wind model (IPWM) (Varney et al. 2014, 2015, 2016a,b) is a fluid model of plasma transport in the high-latitude ionosphere and polar wind covering 97 km to 8400 km altitude in regions poleward of L=4. IPWM solves 8-moment fluid transport equations for the motion of H+, He+, O+(4S), and thermal electrons along magnetic fields lines with outflow boundary conditions at the top of the field lines. IPWM also models the ion production and electron heating from both solar EUV and particle precipitation. The model solves the photochemistry of H+, He+, O+(4S), O+(2D), O+(2P), N+, NO+, N2s+, and O2+ following the chemistry model of Richards (2011) augmented with extra reactions for H+ and He+. As an additional option, IPWM includes a phenomenological treatment of suprathermal ions energized by wave particle interactions (WPI), and the WPI heating parameters can be causally regulated by magnetospheric inputs.

The external inputs required by the model include the EUV spectrum, neutral atmospheric state variables, particle precipitation properties, and the high-latitude convection potential. The model can be run as a stand-alone model using inputs from measurements or empirical models, or as a coupled model taking the required inputs from other physics-based models. As a stand-alone model, the model has been tested using the EUV spectrum from HEUVAC, precipitation from Ovation Prime, convection patterns from SuperDARN, and neutral state variables from NRLMSISE-00.

As part of the MAGE model, IPWM will simulate ionospheric ion outflow into the magnetosphere. To this end, IPWM will be two-way coupled to GAMERA and WACCM-X by taking convection and particle precipitation from REMIX, neutral variables from WACCM-X, and providing outflow variables to GAMERA. REMIX will pass to IPWM multiple different populations of precipitating particles (monoenergetic, diffuse, cusp, and broadband), and the soft populations (cusp and broadband) that are critical drivers of electron heating and ion upflow in IPWM. Additionally, as part of MAGE, IPWM will take additional magnetospheric state variables from GAMERA and REMIX, such as the Alfvénic Poynting flux or the cusp location, to use as causal regulators for models of WPI. As an example, Figure 1 shows the IPWM-simulated parameters of the non-thermal ion population in a storm-time simulation, where IPWM was coupled to the GAMERA predecessor, the Lyon-Fedder-Mobarry (LFM) global magnetosphere code.

IPWM-simulated nonthermal ion in the noon‐midnight plane in a storm-time simulation (Varney et al. 2015). The dayside is to the left. The thick black lines outline the heating region.