A study of observations of Ionospheric upwelling made by theEISCAT Svalbard Radar during the International Polar Year campaign of 2007

We have used EISCAT Svalbard Radar data, obtained during the International Polar Year 2007 campaign, to study ionospheric upflow events with fluxes exceeding 1013 m−2 s−1. In this study, we have classified the upflow events into low, medium, and high flux upflows, and we report on the incidence and seasonal distribution of these different classes. It is observed that high upflow fluxes are comparatively rare and low flux upflow events are a frequent phenomenon. Analysis shows that occurrence peaks around local noon at 31%, 16%, and 2% for low, medium, and high‐flux upflow, respectively, during geomagnetically disturbed periods. In agreement with previous studies on vertical and field‐aligned flows, ion upflow is observed to take place over a wide range of geomagnetic conditions, with downflow flux occurrence being lower than upflow occurrence. In contrast to previous observations, however, the upflow occurrence is greater around noon during highly disturbed geomagnetic conditions than for moderate geomagnetic conditions. Analysis of the seasonal distribution reveals that, while high‐flux upflow has its peak around local noon in the summer, with its occurrence being driven predominantly by high geomagnetic disturbance, the occurrence of low‐flux upflow is broadly distributed across all seasons, geomagnetic activity conditions, and times of day. The medium‐flux upflow events, although distributed across all seasons, show an occurrence peak strongly related to high Kp. Furthermore, during highly disturbed conditions, the low‐flux and medium‐flux upflow events show a minimum occurrence during the winter, whereas minimum occurrence for the high‐flux upflow events occurs in autumn

Jupiter's Atmospheric Variability from Long-term Ground-based Observations at 5 μm

Jupiter's banded structure undergoes strong temporal variations, changing the visible and infrared appearance of the belts and zones in a complex and turbulent way through physical processes that are not yet understood. In this study, we use ground-based 5-μm infrared data captured between 1984 and 2018 by eight different instruments mounted on the Infrared Telescope Facility in Hawai'i and on the Very Large Telescope in Chile to analyze and characterize the long-term variability of Jupiter's cloud-forming region at the 1–4 bar pressure level. The data show a large temporal variability mainly at the equatorial and tropical latitudes, with a smaller temporal variability at mid-latitudes. We also compare the 5-μm-bright and -dark regions with the locations of the visible zones and belts, and we find that these regions are not always colocated, especially in the southern hemisphere. We also present Lomb–Scargle and Wavelet Transform analyses in order to look for possible periodicities of the brightness changes that could help us understand their origin and predict future events. We see that some of these variations occur periodically in time intervals of 4–8 yr. The reasons for these time intervals are not understood, and we explore potential connections to both convective processes in the deeper weather layer and dynamical processes in the upper troposphere and stratosphere. Finally, we perform a Principal Component analysis to reveal a clear anticorrelation on the 5 μm brightness changes between the North Equatorial Belt and the South Equatorial Belt, suggesting a possible connection between the changes in these belts

Origin of the extended Mars radar blackout of September 2017

The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board Mars Express, which operates between 0.1 and 5.5 MHz, suffered from a complete blackout for 10 days in September 2017 when observing on the nightside (a rare occurrence). Moreover, the Shallow Radar (SHARAD) onboard the Mars Reconnaissance Orbiter, which operates at 20 MHz, also suffered a blackout for 3 days when operating on both day and nightsides. We propose that these blackouts are caused by solar energetic particles (SEP) of few tens of keV and above associated with an extreme space weather event between 10 and 22 September 2017, as recorded by the MAVEN mission. Numerical simulations of energetic electron precipitation predict that a lower O2+ nighttime ionospheric layer of magnitude ~1010 m-3 peaking at ~90 km altitude is produced. Consequently, such a layer would absorb radar signals at HF frequencies and explain the blackouts. The peak absorption level is found to be at 70km altitude