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Abstract Radiation Belt Storm Probes (RBSP) data show that seed electrons generated by sub‐storm injections play a role in amplifying chorus waves in the magnetosphere. The wave‐particle interaction leads to rapid heating and acceleration of electrons from 10's of keV to 10's of MeV energies. In this work, we examined the changes in the radiation belt during geomagnetic storm events by studying the RBSP REPT, solar wind, AL, SML, and Dst data in conjunction with the WINDMI model of the magnetosphere. The field‐aligned current output from the model is integrated to generate a proxy E index for various energy bands. These E indices track electron energization from 40 KeV to 20 MeV in the radiation belts. The indices are compared to RBSP data and GOES data. Our proxy indices correspond well to the energization data for electron energy bands between 1.8 and 7.7 MeV. Each E index has a unique empirical loss rate term (τ_L), an empirical time delay term (τ_D), and a gain value, that are fit to the observations. These empirical parameters were adjusted to examine the delay and charging rates associated with different energy bands. We observed that theτ_Landτ_Dvalues are clustered for each energy band.τ_Landτ_Dconsistently increase going from 1.8 to 7.7 MeV in electron energy fluxE_eand the dropout interval increases with increasing energy level. The average trend of Δτ_D/ΔE_ewas 4.1 hr/MeV and the average trend of Δτ_L/ΔE_ewas 2.82 hr/MeV. 

Downconverters, primarily inorganic phosphors, are critical components in white solid-state LED-based lighting and liquid crystal display backlights. Research efforts have led to a fundamental understanding of a downconverter's absorption, photoluminescence, and efficiency as a function of composition, structure, and processing conditions. However, considerably less work has focused on the reliability of phosphors once they are incorporated into LED packages. Solving these issues is often the final step before the commercialization of new materials, but the significant resources and time required to evaluate and mitigate materials failure are rarely discussed in the literature. In this Perspective, we discuss the need for conducting downconverter reliability testing and the potential of accelerating, screening, and understanding downconverter failure modes. Our focus highlights the mechanisms of failure and discusses how this influences materials selection and the design of different LED packages. We also stress the potential for accelerated reliability testing protocols and note the potential role first-principles calculations and data-driven models could play in establishing the compositional-processing trends for different aspects of downconverter reliability. We close with possible research directions that could improve downconverter reliability and emphasize the importance of assessing a material's (chemical) stability where multiple manufacturing and processing steps can dictate system performance. 

Abstract We analyze three substorms that occur on (1) 9 March 2008 05:14 UT, (2) 26 February 2008 04:05 UT, and (3) 26 February 2008 04:55 UT. Using ACE solar wind velocity and interplanetary magnetic fieldB_zvalues, we calculate the rectified (southwardB_z) solar wind voltage propagated to the magnetosphere. The solar wind conditions for the two events were vastly different, 300 kV for 9 March 2008 substorm, compared to 50 kV for 26 February 2008. The voltage is input to a nonlinear physics‐based model of the magnetosphere called WINDMI. The output is the westward auroral electrojet current which is proportional to the auroral electrojet (AL) index from World Data Center for Geomagnetism Kyoto and the SuperMAG auroral electrojet index (SML). Substorm onset times are obtained from the superMAG substorm database, Pu et al. (2010,https://doi.org/10.1029/2009JA014217), Lui (2011,https://doi.org/10.1029/2010JA016078) and synchronized to Time History of Events and Macroscale Interactions during Substorms satellite data. The timing of onset, model parameters, and intermediate state space variables are analyzed. The model onsets occurred about 5 to 10 min earlier than the reported onsets. Onsets occurred when the geotail current in the WINDMI model reached a critical threshold of 6.2 MA for the 9 March 2008 event, while, in contrast, a critical threshold of 2.1 MA was obtained for the two 26 February 2008 events. The model estimates 1.99 PJ of total energy transfer during the 9 March 2008 event, with 0.95 PJ deposited in the ionosphere. The smaller events on 26 February 2008 resulted in a total energy transfer of 0.37 PJ according to the model, with 0.095 PJ deposited in the ionosphere.