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Abstract Using the global Lagrangian version of the piecewise parabolic method‐magnetohydrodynamic (PPMLR‐MHD) model, we simulate two consecutive storms in December 2015, a moderate storm on 14–15 December and a strong storm on 19–22 December, and calculate the radial diffusion coefficients (DLL) from the simulated ultralow frequency waves. We find that even though the strong storm leads to more enhancedBzandEφpower than the moderate storm, the two storms share in common a lot of features on the azimuthal mode structure and power spectrum of ultralow frequency waves. For both storms, the totalBzandEφpower is better correlated with the solar wind dynamic pressure in the storm initial phase and more correlated withAEindex in the recovery phase.Bzwave power is shown to be mostly distributed in low mode numbers, whileEφpower spreads over a wider range of modes. Furthermore, theBzandEφpower spectral densities are found to be higher at higherLregions, with a strongerLdependence in theBzspectra. The estimatedDLLbased on MHD fields shows that inside the magnetopause, the contribution from electric fields is larger than or comparable to that from magnetic fields, and our event‐specific MHD‐basedDLLcan be smaller than some previous empiricalDLLestimations by more than an order of magnitude. At last, by validating against in situ observations from Magnetospheric Multiscale spacecraft, our MHD results are found to generally well reproduce the totalBzfields and wave power for both storms, while theEφpower is underestimated in the MHD simulations.
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New multivariate tests for assessing covariate balance in matched observational studies
Abstract We propose new tests for assessing whether covariates in a treatment group and matched control group are balanced in observational studies. The tests exhibit high power under a wide range of multivariate alternatives, some of which existing tests have little power for. The asymptotic permutation null distributions of the proposed tests are studied and theP‐values calculated through the asymptotic results work well in simulation studies, facilitating the application of the test to large data sets. The tests are illustrated in a study of the effect of smoking on blood lead levels. The proposed tests are implemented in anRpackageBalanceCheck.
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- PAR ID:
- 10364597
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Biometrics
- Volume:
- 78
- Issue:
- 1
- ISSN:
- 0006-341X
- Format(s):
- Medium: X Size: p. 202-213
- Size(s):
- p. 202-213
- Sponsoring Org:
- National Science Foundation
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