Statistical characteristics and the classification of the topside ionospheric mid-latitude trough are systemically analyzed,using observations from the Defense Meteorological Satellite Program F18(DMSP-F18)satellite.The data was obtained at an altitude of around 860 km in near polar orbit,throughout 2013.Our study identified the auroral boundary based on the in-situ electron density and electron spectrum,allowing us to precisely determine the location of the mid-latitude trough.This differs from most previous works,which only use Total Electron Content(TEC)or in-situ electron density.In our study,the troughs exhibited a higher occurrence rate in local winter than in summer,and extended to lower latitudes with increasing geomagnetic activity.It was found that the ionospheric mid-latitude trough,which is associated with temperature changes or enhanced ion drift,exhibited distinct characteristics.Specifically,the ionospheric mid-latitude troughs related to electron temperature(Te)peak were located more equatorward of auroral oval boundary in winter than in summer.The ionospheric mid-latitude troughs related to Te-maximum were less frequently observed at 60−70°S magnetic latitude and 90−240°E longitude.Furthermore,the troughs related to ion temperature(Ti)maximums were observed at relatively higher latitudes,occurring more frequently in winter.In addition,the troughs related to ion velocity(Vi)maximums could be observed in all seasons.The troughs with the maximum-Ti and maximum-Vi were located closer to the equatorward boundary of the auroral oval at the nightside,and in both hemispheres.This implies that enhanced ion drift velocity contributes to increased collisional frictional heating and enhanced ion temperatures,resulting in a density depletion within the trough region.
Dimethylsulfoniopropionate(DMSP)is a compound synthesized by marine phytoplankton that contributes to the oceanic sulfur cycle.Interestingly,DMSP has also been found in algal species and several terrestrial plants,forming part of the global sulfur cycle.However,compared to its role in the marine environment,the impact of DMSP on terrestrial ecosystems remains relatively unexplored.In this study,DMSP was shown to promote longevity and prevent age-associated functional decline in Caenorhabditis elegans(C.elegans),a soil-dwelling organism.DMSP decreased mitochondrial content and improved mitochondrial function in C.elegans at the old stage,which was via enhancing autophagy flux.It was demonstrated that DMSP significantly increased the expression of autophagy and mitophagy genes during aging.Furthermore,DMSP protected against Parkinson’s disease(PD)induced byα-synuclein(α-syn)aggregation via autophagy.Mechanistic studies showed that DMSP directly activated nuclear translocation of the Skinhead-1(SKN-1)transcription factor from the cytoplasm.Moreover,SKN-1 was involved in DMSP-induced autophagy and played a key role in lifespan extension andα-syn clearance in C.elegans.In conclusion,DMSP delays physiological aspects of aging in C.elegans,providing insights into the interplay between the global sulfur cycle and terrestrial organisms.
Hongyuan LiPeng JiYue CaoZhitao CuiJingwei GaoHongshuang WangCong LinYibo WangXiaohui Wang