Data‐Driven Basis Functions for SuperDARN Ionospheric Plasma Flow Characterization and Prediction. Issue 7 (16th July 2021)

• Record Type: Journal Article
• Authors: Shore, R. M.; Freeman, M. P.; Chisham, G.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 7(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-16
• Subjects: SuperDARN -- plasma velocity reanalysis -- empirical orthogonal functions analysis -- ionospheric convection patterns -- data imputation -- polar dynamics; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2021JA029272
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The archive of plasma velocity measurements from the Super Dual Auroral Radar Network (SuperDARN) provides a rich data set for the investigation of magnetosphere‐ionosphere‐thermosphere coupling. However, systematic gaps in this archive exist in space, time, and radar look‐direction. These gaps are generally infilled using climatological averages, spatially smoothed models, or a priori relationships determined from solar wind drivers. We describe a new technique for infilling the data gaps in the SuperDARN archive which requires no external information and is based solely on the SuperDARN measurements. We also avoid the use of climatological averaging or spatial smoothing when computing the infill. In this regard, our approach captures the true variability in the SuperDARN measurements. Our technique is based on data‐interpolating Empirical Orthogonal Function analysis. This method discovers from the SuperDARN data a series of dynamical modes of plasma velocity variation. We compute the modes of a sample month of northern hemisphere winter data, and investigate these in terms of solar wind driving. We find that the B y component of the Interplanetary Magnetic Field (IMF) dominates the variability of the plasma velocity. The IMF B z component is the dominant driver for the background mean field, and a series of non‐leading modes, which describe the two‐cell convection variability, and the substorm. We recommend our new technique for reanalysis investigations of polar‐scale plasma drift phenomena, particularly those with rapid temporal fluctuations and an indirect relationship to the solar wind. Plain Language Summary: Naturally occurring electric fields surround us in near‐Earth space, especially concentrated around the magnetic north and south poles. These electric fields are ultimately driven by the turbulent magnetic field of the Sun, and as such, they are constantly varying. From the Earth's surface, we can measure the electric field disturbances caused by Sun‐Earth interaction, using arrays of radars distributed across the globe. However, not everywhere can be simultaneously measured in this way, and our archive of electric field measurements has many gaps. Because of this, we have until now had to guess at the content of the missing information using quasi‐stationary patterns of electric field, assuming averaged solar conditions. This is known to be a simplification of the true case. In this study, we develop and apply a pattern‐finding technique, which allows us the best‐yet determination of the true nature of near‐Earth space electric field variability. Key Points: Underlying modes of ionospheric plasma flow velocity discovered using novel Empirical Orthogonal Function infill technique tailored to non‐orthogonal Super Dual Auroral Radar Network data Plasma velocity modes similar to those of surface magnetic field variation, with a different hierarchy of mode importance Interplanetary Magnetic Field (IMF) B y has a stronger impact on plasma velocity variability than IMF B z, which is opposite to the magnetic field variability behavior