[1] We report on a rare ultra-low-frequency (ULF) wave generation event associated with the formation of a plasmasphere boundary layer (PBL), which was well observed by one of the THEMIS satellites, TH-D, during subsequent outbound passes. On 13 September 2011, TH-D observed a sharp plasmapause at L = 3.4. The plasmasphere started to expand and continued to be refilled on 14 September. On 15 September, a PBL was formed with two density gradients at L = 4.4 and 6.5, respectively. Within the two density gradients, strong radial magnetic field and azimuthal electric field oscillations were observed, suggesting poloidal ULF waves. Based on the phase delay between magnetic and electric field signals, as well as the comparison between the observed wave frequency and predicted harmonic eigenfrequency, we find that the observed oscillations are second harmonic poloidal waves. Further investigation shows that the observed waves are likely generated by drift-bounce resonance with "bump-on-tail" plasma distributions at~10 keV. We demonstrate that the waves are excited within the PBL where the eigenfrequency is close to the bounce frequency of these hot protons, but not outside the PBL where the eigenfrequency deviates from the bounce frequency. Finally, we suggest that cold plasma density seems to be a controlling factor for ULF wave generation as well, in addition to the bump-on-tail energy source, by altering eigenfrequency of the local field lines.

The human ubiquitin C-terminal hydrolase, UCH-L1, is an abundant neuronal deubiquitinase that is associated with Parkinson's disease. It contains a complex Gordian knot topology formed by the polypeptide chain alone. Using a combination of fluorescence-based kinetic measurements, we show that UCH-L1 has two distinct kinetic folding intermediates that are transiently populated on parallel pathways between the denatured and native states. NMR hydrogen-deuterium exchange (HDX) experiments indicate the presence of partially unfolded forms (PUFs) of UCH-L1 under native conditions. HDX measurements as a function of urea concentration were used to establish the structure of the PUFs and pulse-labelled HDX NMR was used to show that the PUFs and the folding intermediates are likely the same species. In both cases, a similar stable core encompassing most of the central β-sheet is highly structured and α-helix 3, which is partially formed, packs against it. In contrast to the stable β-sheet core, the peripheral α-helices display significant local fluctuations leading to rapid exchange. The results also suggest that the main difference between the two kinetic intermediates is structure and packing of α-helices 3 and 7 and the degree of structure in β-strand 5. Together, the fluorescence and NMR results establish that UCH-L1 neither folds through a continuum of pathways nor by a single discrete pathway. Its folding is complex, the β-sheet core forms early and is present in both intermediate states, and the rate-limiting step which is likely to involve the threading of the chain to form the 52-knot occurs late on the folding pathway.

We report the in situ observation of a plasma vortex induced by a solar wind dynamic pressure enhancement in the nightside plasma sheet using multipoint measurements from Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. The vortex has a scale of 5-10 Re and propagates several Re downtail, expanding while propagating. The features of the vortex are consistent with the prediction of the Sibeck (1990) model, and the vortex can penetrate deep (~8 Re) in the dawn-dusk direction and couple to field line oscillations. Global magnetohydrodynamics simulations are carried out, and it is found that the simulation and observations are consistent with each other. Data from THEMIS ground magnetometer stations indicate a poleward propagating vortex in the ionosphere, with a rotational sense consistent with the existence of the vortex observed in the magnetotail.