SuperDARN assimilative mapping

Cousins, E. D. P.; Matsuo, Tomoko; Richmond, A. D.

doi:10.1002/2013ja019321

Cited by 43 publications

(68 citation statements)

References 11 publications

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“…EOFs of the Hall and Pedersen conductances, herein represented using the polar cap spherical harmonics basis, are obtained by a sequential nonlinear regression analysis of observations along DMSP satellite trajectories and ordered by their variance. These EOFs and their amplitudes can be used to describe the spatial and temporal coherence of the Pedersen and Hall conductances in a manner similar to that reported by Matsuo et al [, ] and Cousins et al [, ] for electric field variability and Cousins et al [, ] for field‐aligned current variability. Our results allow for improved modeling of the background error covariance needed for ionospheric assimilative procedures [ Richmond and Kamide , ; Matsuo et al , ].…”

Section: Introductionmentioning

confidence: 77%

Modes of high‐latitude auroral conductance variability derived from DMSP energetic electron precipitation observations: Empirical orthogonal function analysis

et al. 2015

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We provide the first ever characterization of the primary modes of ionospheric Hall and Pedersen conductance variability as empirical orthogonal functions (EOFs). These are derived from six satellite years of Defense Meteorological Satellite Program (DMSP) particle data acquired during the rise of solar cycles 22 and 24. The 60 million DMSP spectra were each processed through the Global Airlglow Model. Ours is the first large‐scale analysis of ionospheric conductances completely free of assumption of the incident electron energy spectra. We show that the mean patterns and first four EOFs capture ∼50.1 and 52.9% of the total Pedersen and Hall conductance variabilities, respectively. The mean patterns and first EOFs are consistent with typical diffuse auroral oval structures and quiet time strengthening/weakening of the mean pattern. The second and third EOFs show major disturbance features of magnetosphere‐ionosphere (MI) interactions: geomagnetically induced auroral zone expansion in EOF2 and the auroral substorm current wedge in EOF3. The fourth EOFs suggest diminished conductance associated with ionospheric substorm recovery mode. We identify the most important modes of ionospheric conductance variability. Our results will allow improved modeling of the background error covariance needed for ionospheric assimilative procedures and improved understanding of MI coupling processes.

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Section: Introductionmentioning

confidence: 77%

Modes of high‐latitude auroral conductance variability derived from DMSP energetic electron precipitation observations: Empirical orthogonal function analysis

et al. 2015

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“…The time‐dependent coefficients

{\overset{true¯}{bold-italicα}}_{j}

corresponding to the averaged EOFs at time j are set to minimize the cost function that accounts for deviation from both the observations and the background model, as discussed in Cousins et al (). The best fit

{\overset{true¯}{bold-italicα}}_{j}

can be calculated as

{\overset{true¯}{bold-italicα}}_{j} = boldK ()(, δ \overset{B}{true} ()(,,, t_{j}, ϕ_{i}, λ_{i}) - δ {\overset{true\to}{normalB}}^{(italicmean)} ()(,, ϕ_{i}, λ_{i}))

boldK = {[{()(, boldH \overset{G}{true})}^{normalT} {boldR}^{- 1} (H \overset{true¯}{boldG}) + {boldC}_{normala}^{- 1}]}^{- 1} {(H \overset{true¯}{boldG})}^{T} R^{- 1}

…”

Section: Methodsmentioning

confidence: 99%

Modes of (FACs) Variability and Their Hemispheric Asymmetry Revealed by Inverse and Assimilative Analysis of Iridium Magnetometer Data

et al. 2020

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We determine the primary modes of field‐aligned current (FAC) variability and their hemispheric asymmetry by nonlinear regression analysis of a multiyear global data set of Iridium constellation engineering‐grade magnetometer data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment program. The spatial and temporal FAC variability associated with three major categories of solar wind drivers, (1) slow flow, (2) high‐speed streams (HSS), (3) transient flow related to coronal mass ejections (CMEs), and (4) a combination of these, is characterized as empirical orthogonal functions (EOFs) and their time‐varying amplitude. For the combined solar wind category, the order of the modes of variability are strengthening/weakening of (1) EOF1—all FACs; (2) EOF2—Region 2 (R2) FACs; and (3) EOF3—dayside/nightside FACs. The first two EOFs are associated with solar wind coupling; EOF3 is associated with the ecliptic components of the interplanetary magnetic field (IMF). We also find hemispheric asymmetry in FACs. Northern Hemisphere EOFs show clearer spatial features and higher correlation coefficients with solar wind drivers. The Northern Hemisphere also shows higher correlation coefficients in all seasons except winter. We find transient flow EOFs to be better correlated with solar wind drivers such as IMF Bz and coupling functions, while HSS EOFs are better correlated with solar wind plasma parameters. CME‐related transient flow EOFs also show R2 FAC variabilities that are not found in other separate wind drivers. Application of the EOF analysis to the Iridium magnetometer data shows significant promise for greater understanding of geoeffectiveness of solar wind interactions with geospace.

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“…As with SuperDARN observations, the AMPERE observational errors are assumed to be independent in order to keep the error covariance matrix diagonal and keep the analysis tractable. Also, following Cousins et al [], the observational error variances are scaled by a constant factor at each time step depending on the number of observations available, with the scaling factor given by

\sqrt[4]{L}

, where L is the number of observations. This factor is ∼4 and ∼8 for standard and high‐rate data, respectively, and accounts for components of observational error not captured by the variability‐based estimate (e.g., measurement errors) and helps prevent overweighting of the high‐rate AMPERE data, which have a small spatial resolution compared with that of the analysis described in this study and are not likely independent as assumed previously.…”

Section: Assimilation Proceduresmentioning

confidence: 99%

Mapping high‐latitude ionospheric electrodynamics with SuperDARN and AMPERE

2015

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An assimilative procedure for mapping high-latitude ionospheric electrodynamics is developed for use with plasma drift observations from the Super Dural Auroral Radar Network (SuperDARN) and magnetic perturbation observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). This procedure incorporates the observations and their errors, as well as two background models and their error covariances (estimated through empirical orthogonal function analysis) to infer complete distributions of electrostatic potential and vector magnetic potential in the high-latitude ionosphere. The assimilative technique also enables objective error analysis of the results. Various methods of specifying height-integrated ionospheric conductivity, which is required by the procedure, are implemented and evaluated quantitatively. The benefits of using both SuperDARN and AMPERE data to solve for both electrostatic and vector magnetic potentials, rather than using the data sets independently or solving for just electrostatic potential, are demonstrated. Specifically, solving for vector magnetic potential improves the specification of field-aligned currents (FACs), and using both data sets together improves the specification of features in regions lacking one type of data (SuperDARN or AMPERE). Additionally, using the data sets together results in a better correspondence between large-scale features in the electrostatic potential distribution and those in the FAC distribution, as compared to using SuperDARN data alone to infer electrostatic potential and AMPERE data alone to infer FACs. Finally, the estimated uncertainty in the results decreases by typically ∼20% when both data sets rather than just one are included.

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SuperDARN assimilative mapping

Cited by 43 publications

References 11 publications

Modes of high‐latitude auroral conductance variability derived from DMSP energetic electron precipitation observations: Empirical orthogonal function analysis

Modes of high‐latitude auroral conductance variability derived from DMSP energetic electron precipitation observations: Empirical orthogonal function analysis

Modes of (FACs) Variability and Their Hemispheric Asymmetry Revealed by Inverse and Assimilative Analysis of Iridium Magnetometer Data

Mapping high‐latitude ionospheric electrodynamics with SuperDARN and AMPERE

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