Statistical Auroral Absorption Model Parameterized by AE Index

Abstract Energetic electron precipitation, often in association with enhanced geomagnetic activity, leads to increased D‐region ionization in the auroral region causing auroral absorption. A statistical auroral absorption model is presented for high‐latitudes (poleward of 50° magnetic latitude) based on data collected from 2010 to 2019 from 13 wide‐beam riometers at 30 MHz spanning 53.9°–86.9° magnetic latitude. Hourly maximum absorption values were sorted into bins of 5° magnetic latitude and 1 hr of magnetic local time and parameterized based on the hourly maximum global AE index for 0–100 nT, 100–200 nT, 200–300 nT, 300–400 nT, 400–500 nT, 500–600 nT, 600–800 nT, 800–1,000 nT, and ≥1,000 nT. The model uses spherical cap harmonic analysis with a maximum degree index and order of 12 and 10, respectively. Absorption is characterized by a dawnside enhancement that peaks in the pre‐noon sector and spreads toward the midnight sector with increasing geomagnetic activity. The maximum equatorward and poleward extents of absorption >0.5 dB expand at a rate of 1.4°/100 nT and 0.4°/100 nT, respectively. According to this model, >0.5 dB absorption is expected in >10% of the high‐latitude region for AE > 500 nT (occurs 23.6% of times), and 40% of the high‐latitude region for AE ≥ 1,000 nT (occurs 3.2% of times). The statistical auroral absorption model may be used as a background model as a constraint for modeling instantaneous auroral absorption.