Assimilation of GNSS Measurements for Estimation of High‐Latitude Convection Processes

• Published in: Space Weather 2020-07, Vol.18 (8), p.n/a
• Main Authors: Miladinovich, Daniel S., Datta‐Barua, Seebany, López Rubio, Aurora, Zhang, Shun‐Rong, Bust, Gary S.
• Format: Article
• Language: English
• Subjects: Atmosphere; Basis functions; Charged particles; Convection; Convection processes; coupling; Data assimilation; Data collection; Dipoles; Electric fields; Electric potential; Electrodynamics; Electron density; Geomagnetic storms; Geomagnetism; Global navigation satellite system; Incoherent scatter radar; Interferometers; ionosphere; Ionospheric electron content; Ionospheric models; Ionospheric plasma; Latitude; Magnetic fields; Magnetic storms; Navigation satellites; Navigation systems; Neutral particles; Parameter estimation; Particle density (concentration); Plasma; Plasma density; Plasma drift; Reverse engineering; Spherical harmonics; Storms; subauroral polarization stream; Temperature variations; thermosphere; Upper atmosphere; Wind; Wind effects; Wind measurement; Wind power generation
• ISSN: 1542-7390; 1539-4964; 1542-7390
• DOI: 10.1029/2019SW002409

Geomagnetic storms produce significant electrodynamics at midlatitudes. Strong ion convection can affect thermospheric neutral wind motion. The converse is also true, such that both fields and winds can drive ionospheric plasma movement. This work adjusts a background modeled high‐latitude electrostatic potential to estimate the storm time electric field based on data‐derived plasma densities and measurements of neutral wind. Electron densities are derived from global navigation satellite system (GNSS) total electron content measurements using Ionospheric Data Assimilation Four‐Dimensional (IDA4D). These are input to Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE) to estimate electric potential corrections to the background Weimer 2000 potential model. The EMPIRE basis functions for electric potential are spherical harmonics in dipole magnetic colatitude and longitude, enforced to be constant along a magnetic field line. For the 17 March 2015 storm, EMPIRE electric potential produces westward zonal ion drifts that more closely agree with incoherent scatter radar (ISR) measurements made at Millstone Hill than the background Weimer 2000 model alone, when electric potential and meridional neutral winds are both corrected. Additionally ingesting northward line‐of‐sight neutral wind measurements from a Fabry‐Perot interferometer at Millstone Hill makes little difference in the agreement between zonal ion drift predictions and measurements. Estimation of only electric potential reduces the agreement between the assimilated prediction of the field‐perpendicular zonal drifts and ISR measurements significantly. Plain Language Summary Charged particles and neutral particles in our upper atmosphere respond to different forces. Plasma drifts in response to electric and magnetic fields; neutrals winds blow due to pressure and temperature variations. Because they coexist in the upper atmosphere, plasma and neutral particles interact in ways we do not always understand, especially during geomagnetic storms. This study investigates how using measurements of charged particle density can help us deduce what the storm time forces were. We use time‐lapse images of the plasma density to try to estimate what the electric field that moved the plasma was during a storm. We also examine how stronger neutral winds influence the estimated effect of the electric field and whether a limited number of measurements of the neutral winds help constrain both the n