Microstructural and magnetic characterization were undertaken on high-rate, high-temperature grown YBa2Cu3O7–δ (YBCO) films. The films were of approximately 1 μm thickness and were grown by pulsed laser deposition on (100) SrTiO3 using a high-power industrial laser at growth temperatures between 750 °C and 870 °C and at growth rates of up to 4 μm/min. Two YBCO layers with different c-lattice parameters were observed in the films, the higher c value occurring near the substrate interface and arising from cation disorder and oxygen nonstoichiometry, and the lower one near the film surface arising from cation disorder alone. BaCuO2 precipitates were present near the surface of the films, indicative of partial melting during growth. The amount of BaCuO2 increased with growth temperature. Epitaxial Y2O3 also formed in increasing amounts suggestive of a different partial melting reaction in the films compared to bulk YBCO, where Y2BaCuO5 coexists with liquid. Around 1 MA/cm2 values of high critical current density (Jc) were observed in the films, and the in-field Jc improved with growth temperature despite the fact that the superconducting transition width increased significantly.

Rapid onset (few ms), rapid decay (~ls) perturbations or RORDs occur frequently on the west-to-east signal from NWC to Dunedin, more often than not with classic Trimpis. They do not appear on an NWC mimic signal directly injected into the antenna and so cannot be broadband bursts. There is no delay between the initiating sferic and RORD start, implying that they are produced not by whistler-induced electron precipitation but directly by lightning. Observations on a multi element array show that classic Trimpis and RORDs initiated by the same sferic usually come from measurably different directions, so the lightning-induced ionisation enhancements (LIEs) which cause them must be laterally displaced. They may also be vertically displaced to explain the differing decay rates (30s versus 1 s). We conclude that RORDs are VLF echoes from vertical columns of ionisation at around 40km altitude and having vertical dimensions of some tens of km and horizontal dimensions of 1–2km, since such a column would scatter sufficient signal to fit observed amplitudes. Cloud-to-ionosphere (CID) lightning discharges (also called “cloud-to-space” and “cloud-to-stratosphere” discharges) of these visible dimensions have been observed on mountain observatories and on board the Space Shuttle.