High-latitude environments show extreme seasonal variation in physical and biological variables. The classic paradigm of Arctic marine ecosystems holds that most biological processes slow down or cease during the polar night. One key process that is generally assumed to cease during winter is diel vertical migration (DVM) of zooplankton. DVM constitutes the largest synchronized movement of biomass on the planet, and is of paramount importance for marine ecosystem function and carbon cycling. Here we present acoustic data that demonstrate a synchronized DVM behaviour of zooplankton that continues throughout the Arctic winter, in both open and ice-covered waters. We argue that even during the polar night, DVM is regulated by diel variations in solar and lunar illumination, which are at intensities far below the threshold of human perception. We also demonstrate that winter DVM is stronger in open waters compared with ice-covered waters. This suggests that the biologically mediated vertical flux of carbon will increase if there is a continued retreat of the Arctic winter sea ice cover.

[1] Eight years of meridian scanning photometer data from Ny-Å lesund, Svalbard have been analyzed to study the occurrence of F region polar cap patches at night. In total 333 patches in 43 days were observed to hit the poleward boundary of nighttime auroras which is a unique signature of ongoing tail reconnection. The MLT distribution of patches is smooth and exhibit a bell shaped function symmetric around 23:25 MLT. The symmetry of the patch distribution about midnight indicates that patches populate the morning cell and the dusk cell of polar cap convection at the same probability. About 60% of the patches exit the polar cap from 22-01 MLT, but the entire distribution span from 18:30-04:50 MLT, i.e., nearly the full MLT span where tail reconnection may occur. The patch occurrence statistics presented here is an important new result of relevance to phenomena related to the presence and transport of patches. Citation: Moen, J., N.

We present two examples from the cusp ionosphere over Svalbard, where poleward moving auroral forms (PMAFs) are causing significant phase scintillation in signals from navigation satellites. The data were obtained using a combination of ground‐based optical instruments and a newly installed multiconstellation navigation signal receiver at Longyearbyen. Both events affected signals from GPS and Global Navigation Satellite System (GLONASS). When one intense PMAF appeared, the signal from one GPS spacecraft also experienced a temporary loss of signal lock. Although several polar cap patches were also observed in the area as enhancements in total electron content, the most severe scintillation and loss of signal lock appear to be attributed to very intense PMAF activity. This shows that PMAFs are locations of strong ionospheric irregularities, which at times may cause more severe disturbances in the cusp ionosphere for navigation signals than polar cap patches.

[1] In this study we present optical ground-based signatures of drifting airglow patches in the polar ionospheric F-layer, in the evening/nighttime MLT sector. The patches were observed under predominately IMF B Z < 0, IMF B Y > 0 conditions, which are favorable for highdensity sunlit plasma to be entrained into the polar cap with the large afternoon cell in the northern hemisphere. The patch morphology, such as altitude, meridional convection speed, and repetition rate was investigated using a meridian scanning photometer, and put into the context of activity changes in the auroral substorm. It was found that the meridional patch speed was modulated by the ongoing substorms, and that the patches crossed the open/closed field line boundary (OCB), even during late recovery, and subsequent growth phase. We take this as an indication of ongoing tail reconnection, and we therefore propose that the patches can be used as a tracer for tail reconnection when they cross the OCB and enter the nighttime auroral oval.

[1] The Investigation of Cusp Irregularities 2 sounding rocket was launched 5 December 2008 at 1035 UT. We present an overview of the associated solar wind and auroral conditions, and we look in detail at the relationship between poleward moving auroral forms (PMAFs) and the creation of polar cap patches using ground-based optical and radar data as well as in situ data from the rocket payload. The solar wind was found to be dominated by a stable interplanetary magnetic field (IMF) B z < 0 and by an IMF B y > 0 situation. The aurora was characterized by a series of PMAFs throughout the period of interest. Associated with each PMAF were polar cap patches seen to emerge from the most poleward location of the PMAFs. On the basis of the available data, we present a conceptual model explaining the creation of the polar cap patches under the given solar wind and ionospheric conditions.