Ion pickup observed at comet 67P with the Rosetta Plasma Consortium (RPC) particle sensors: similarities with previous observations and AMPTE releases, and effects of increasing activity

Rosetta’s unique trajectory is allowing exciting measurements of the development of cometary activity between ~3.6 and 1.2 AU for the first time. For a few months following Rosetta’s arrival at comet 67P in August 2014, data from the Rosetta Plasma Consortium (RPC) particle instruments (the Ion and Electron Spectrometer (IES) and the Ion Composition Analyser (ICA)), have shown that the low activity cometary environment was initially dominated by the solar wind. This was expected in the early stages of the mission. In addition to the solar wind and related He+ populations, a low energy pickup ion population is seen intermittently in the early phase of the mission near the comet. The population is very time dependent, but at times reaches higher energy approaching the solar wind energy. During these intervals, ICA data indicate that the composition is mainly water group ions. The rising energy signatures of these ions observed at times indicate that they are in the early phases of the pickup process, initially accelerated by the electric field (‘early phase pickup’). Here, we compare these exciting pickup ion measurements with Giotto measurements at the relatively weak (compared to Halley) comet Grigg-Skjellerup, where early phase pickup was seen including non-gyrotropic cometary ions, and with the AMPTE lithium and barium releases. Our results reveal some striking similarities with the AMPTE releases, particularly the rising energy signature related to early pickup, and a momentum balance between the pickup ions and the deflected solar wind. There is also evidence for momentum transfer between the pickup ions and the solar wind, with less velocity change seen in the solar wind alpha particles compared to the protons; this was also observed in an AMPTE lithium release. We discuss the effects of increasing activity observed between 3.6 to 1.8 AU, including the increasing dominance and energisation of pickup ions, increasing ionospheric effects and the decreasing effect of the solar wind

A new concept for estimating the influence of vegetation on throughfall kinetic energy using aerial laser scanning

Soil loss caused by erosion has enormous economic and social impacts. Splash effects of rainfall are an important driver of erosion processes; however, effects of vegetation on splash erosion are still not fully understood. Splash erosion processes under vegetation are investigated by means of throughfall kinetic energy (TKE). Previous studies on TKE utilized a heterogeneous set of plant and canopy parameters to assess vegetation’s influence on erosion by rain splash but remained on individual plant- or plotlevels. In the present study we developed a method for the area-wide estimation of the influence of vegetation on TKE using remote sensing methods. In a literature review we identified key vegetation variables influencing splash erosion and developed a conceptual model to describe the interaction of vegetation and raindrops. Our model considers both amplifying and protecting effect of vegetation layers according to their height above the ground and aggregates them into a new indicator: the Vegetation Splash Factor (VSF). It is based on the proportional contribution of drips per layer, which can be calculated via the vegetation cover profile from airborne LiDAR datasets. In a case study, we calculated the VSF using a LiDAR dataset for La Campana National Park in central Chile. The studied catchment comprises a heterogeneous mosaic of vegetation layer combinations and types and is hence well suited to test the approach.We calculated a VSF map showing the relation between vegetation structure and its expected influence on TKE. Mean VSF was 1.42, indicating amplifying overall effect of vegetation on TKE that was present in 81% of the area. Values below 1 indicating a protective effect were calculated for 19% of the area. For future work, we recommend refining the weighting factor by calibration to local conditions using field-reference data and comparing the VSF with TKE field measurements

A Sustainability Index for Small Island Developing States

This paper proposes a novel approach to measuring the progress of small island developing states (SIDS) towards sustainable development (SD) as set by the UN Sustainable Development Goals 2030. Currently, these goals do not provide adequate guidance on how countries might measure their progress towards sustainability. We use these goals and a subset of their targets to develop an index with concrete targets, through the use of pertinent sustainability indicators, that SIDS should aim to achieve a sustainable society. In addition to the three categorical pillars of SD (social, economic and environmental), we included the category Climate Change and Disaster Management (incorporating Disaster Risk Reduction). The basis of our decision is that the UN and the Intergovernmental Panel on Climate Change have both recognized the vulnerability of SIDS to both environmental hazards. Our index scores a total 70 individual indicators for the four categories to track the progress of a SIDS towards a sustainable society. Using the Caribbean nation, Republic of Trinidad and Tobago, as our SIDS case study, we report the average of the scores for each category to illustrate its progress towards sustainability. Overall Trinidad and Tobago is slowly progressing towards a more sustainably developed society. Our results show that the nation is only moderately successful regarding progress in three traditional pillars of SD, social, economic and environmental. However, Trinidad and Tobago scores poorly in the Climate Change and Disaster Management category and needs to improve in this area especially due to its vulnerability