Geospace Concussion: Global Reversal of Ionospheric Vertical Plasma Drift in Response to a Sudden Commencement.

An interplanetary shock can abruptly compress the magnetosphere, excite magnetospheric waves and field-aligned currents, and cause a ground magnetic response known as a sudden commencement (SC). However, the transient (<∼1 min) response of the ionosphere-thermosphere system during an SC has been little studied due to limited temporal resolution in previous investigations. Here, we report observations of a global reversal of ionospheric vertical plasma motion during an SC on 24 October 2011 using ∼6 s resolution Super Dual Auroral Radar Network ground scatter data. The dayside ionosphere suddenly moved downward during the magnetospheric compression due to the SC, lasting for only ∼1 min before moving upward. By contrast, the post-midnight ionosphere briefly moved upward then moved downward during the SC. Simulations with a coupled geospace model suggest that the reversed E ⃗ × B ⃗ vertical drift is caused by a global reversal of ionospheric zonal electric field induced by magnetospheric compression during the SC.

Comparison of SuperDARN peak electron density estimates based on elevation angle measurements to ionosonde and incoherent scatter radar measurements.

Measurements of the electron density at the F region peak by the Canadian Advanced Digital Ionosonde (CADI) and the Resolute Incoherent Scatter Radar (RISR) are used to assess the quality of peak electron density estimates made from elevation angle measurements by the Super Dual Auroral Radar Network (SuperDARN) high-frequency radar at Rankin Inlet (RKN). All three instruments monitor the ionosphere near Resolute Bay. The CADI-RKN joint dataset comprises measurements between 2008 and 2017 while RISR-RKN dataset covers about 60 daylong events in 2016. Reasonable agreement between the RKN estimates and measurements by CADI and RISR is shown. Two minor discrepancies are discussed: RKN radar daytime peak electron density overestimation by ~ 10% and underestimation by up to 30% in other time sectors. In winter nighttime and dawn, cases were identified in which the RKN radar significantly overestimates the peak electron density. This occurs when the phase in the RKN interferometer measurements is incorrectly shifted by 2 π , and this is most significant when electron densities are low. Statistical fitting to the joint data sets, split into four time sectors of a day, has been done and parameters of the fit have been determined. These allow slight adjustment of measured real-time RKN values to better reflect real peak electron densities in the ionosphere within its field of view.

Visualization of rapid electron precipitation via chorus element wave-particle interactions.

Chorus waves, among the most intense electromagnetic emissions in the Earth's magnetosphere, magnetized planets, and laboratory plasmas, play an important role in the acceleration and loss of energetic electrons in the plasma universe through resonant interactions with electrons. However, the spatial evolution of the electron resonant interactions with electromagnetic waves remains poorly understood owing to imaging difficulties. Here we provide a compelling visualization of chorus element wave-particle interactions in the Earth's magnetosphere. Through in-situ measurements of chorus waveforms with the Arase satellite and transient auroral flashes from electron precipitation events as detected by 100-Hz video sampling from the ground, Earth's aurora becomes a display for the resonant interactions. Our observations capture an asymmetric spatial development, correlated strongly with the amplitude variation of discrete chorus elements. This finding is not theoretically predicted but helps in understanding the rapid scattering processes of energetic electrons near the Earth and other magnetized planets.

Formation mechanisms of melanoidins and fluorescent pyridinium compounds as advanced glycation end products.

The formation mechanisms of melanoidins as advanced glycation end products (AGEs) have not been resolved. Blue and red pigments generated in the D-xylose-glycine reaction system are postulated to be intermediate oligomers in the generation of melanoidins. A novel blue pigment, designated blue-M5, was identified as a similar structure to blue-M1 except for the side chain of two dihydroxypropyl groups. Blue pigments were also generated in the D-glucose-glycine and D-xylose-beta-alanine reaction systems as well as in the D-xylose-glycine reaction system. Blue pigments by the Maillard reaction might be formed by the decarboxylation of two molecules of pyrrolopyrrole-2-carbaldehydes (PPA). PPA, composed of a side chain of a dihydroxypropyl group, was identified as a precursor of blue pigments. In fact, blue-M5 was generated by the incubation of PPA alone. Blue pigments, which involved pyrrolopyrrole structures, were readily changed to brown polymers. Glyceraldehyde-derived pyridinium (GLAP) compound, a glyceraldehyde-derived fluorescent AGE, and lysyl-pyrropyridine, a 3-deoxyglucosone-derived fluorescent AGE, were detected at higher levels in the plasma proteins and the tail tendon collagen of streptozotocin-induced diabetic rats compared to normal rats. GLAP and lysyl-pyrropyridine, therefore, might be related to the progression of diabetic complications.