Empirical Model of Precipitating Ion Oval. Issue 10 (26th October 2017)

• Record Type: Journal Article
• Authors: Goldstein, Jerry
• Is Part Of: Journal of geophysical research. Volume 122:Issue 10(2017)
• Page Start: 10, 458
• Page End: 10, 471
• Publication Date: 2017-10-26
• Subjects: modeling -- ion precipitation -- auroral oval; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2017JA024622
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: In this brief technical report published maps of ion integral flux are used to constrain an empirical model of the precipitating ion oval. The ion oval is modeled as a Gaussian function of ionospheric latitude that depends on local time and the K p geomagnetic index. The three parameters defining this function are the centroid latitude, width, and amplitude. The local time dependences of these three parameters are approximated by Fourier series expansions whose coefficients are constrained by the published ion maps. The K p dependence of each coefficient is modeled by a linear fit. Optimization of the number of terms in the expansion is achieved via minimization of the global standard deviation between the model and the published ion map at each K p . The empirical model is valid near the peak flux of the auroral oval; inside its centroid region the model reproduces the published ion maps with standard deviations of less than 5% of the peak integral flux. On the subglobal scale, average local errors (measured as a fraction of the point‐to‐point integral flux) are below 30% in the centroid region. Outside its centroid region the model deviates significantly from the H89 integral flux maps. The model's performance is assessed by comparing it with both local and global data from a 17 April 2002 substorm event. The model can reproduce important features of the macroscale auroral region but none of its subglobal structure, and not immediately following a substorm. Plain Language Summary: This brief technical report provides an empirical model of ions in the auroral oval. The model is based on published statistical maps of auroral ions. The empirical model is tested against two sets of observations (both local/in situ and global images) from the same auroral substorm event on 17 April 2002. The model has limitations but is useful to represent the macroscale auroral region. Key Points: Published maps of average ion integral flux used to constrain empirical model of precipitating ion oval Empirical model reproduces average ion precipitation with standard deviations under 5% of peak integral flux In data‐model comparisons, model reproduces important macroscale features but not subglobal structure or substorm dynamics