简介：Low-frequencychorusemissionshaverecentlyattractedmuchattentionduetothesuggestionthattheymayplayimportantrolesinthedynamicsoftheVanAllenBelts.However,themechanism(s)generatingtheselow-frequencychorusemissionshavenotbeenwellunderstood.Inthisletter,wereportaninterestingcaseinwhichbackgroundplasmadensityloweredthelowercutofffrequencyofchorusemissionsfromabove0.1fce(typicalordinarychorus)to0.02fce(extremelylow-frequencychorus).Thoseextremelylow-frequencychoruswaveswereobservedinaratherdenseplasma,wherethenumberdensityNewasfoundtobeseveraltimeslargerthanhasbeenassociatedwithobservationsofordinarychoruswaves.Forsuprathermalelectronswhosefreeenergyissuppliedbyanisotropictemperatures,lineargrowthrates(calculatedusingin-situplasmaparametersmeasuredbytheVanAllenProbes)showthatwhistlermodeinstabilitycanoccuratfrequenciesbelow0.1fcewhenthebackgroundplasmadensityNeincreases.EspeciallywhenNereaches90cm^-3ormore,thelowestunstablefrequencycanextendto0.02fceorevenless,whichisconsistentwithsatelliteobservations.Therefore,ourresultsdemonstratethatadensebackgroundplasmacouldplayanessentialroleintheexcitationofextremelylowfrequencychoruswavesbycontrollingthewavegrowthrates.

简介：Usingfoursatellitedatasets(TOMS/SBUV,OMI,MLS,andHALOE),weanalyzetheseasonalvariationsofthetotalcolumnozone(TCO)anditszonaldeviation(TCO*),andrevealtheverticalstructureoftheOzoneLow(OV)overtheAsiancontinent.Ourprincipalfindingsare:(1)TheTCOovertheAsiancontinentreachesitsmaximuminthespringanditsminimumintheautumn.TheOzoneLowexistsfromMaytoSeptember.(2)TheOzoneLowhastwonegativecores,locatedinthelowerandtheupperstratosphere.Thelowercoreisnear30hPainthewinterand70hPaintheotherseasons.Theuppercorevariesfrom10hPato1hPaamongthefourseasons.(3)ThepositionoftheOzoneLowinthelowerandtheupperstratosphereovertheAsiancontinentshowsseasonalvariability.

简介：Observationsofaquasi-90-dayoscillationinthemesosphereandlowerthermosphere(MLT)regionfromApril2011toDecember2014arepresentedinthisstudy.Thereisclearevidenceofaquasi-90-dayoscillationintemperaturesobtainedfromtheKunmingmeteorradar(25.6°N,103.8°E)andSoundingoftheAtmosphereusingBroadbandEmissionRadiometry(SABER),aswellasinwindobservedbytheKunmingmeteorradar.Thequasi-90-dayoscillationappearstobeaprominentfeatureinthetemperaturesandmeridionalwindtidesandpresentsquiteregularcyclesthatoccurapproximatelytwiceperyear.Theamplitudesandphasesofthequasi-90-dayoscillationintheSABERtemperatureshowafeaturesimilartothatofupward-propagateddiurnaltides,whichhaveaverticalwavelengthof~20kmabove70km.Intheloweratmosphere,asimilar90-dayvariabilityispresentedinthesurfacelatentheatfluxandcorrelateswiththetemperatureintheMLTregion.Similartothequasi-90-dayoscillationintemperature,a90-dayvariabilityofozone(O3)isalsopresentintheMLTregionandisconsideredtobedrivenbyasimilarvariabilityintheupwardly-propagateddiurnaltidesgeneratedintheloweratmosphere.Moreover,the90-dayvariabilityintheabsorptionofultraviolet(UV)radiationbydaytimeO3intheMLTregionisaninsitusourceofthequasi-90-dayoscillationintheMLTtemperature.

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简介：Amapoftheaverageatomicnumberoflunarrockandsoilcanbeusedtodifferentiatelithologyandsoiltypeonthelunarsurface.Thispaperestablishesalinearrelationshipbetweentheaverageatomicnumberoflunarrockorsoilandthefluxofpositionannihilationradiation(0.512-MeVgamma-ray)fromthelunarsurface.TherelationshipisconfirmedbyMonteCarlosimulationwithdatafromlunarrockorsoilsamplescollectedbyLuna(Russia)andApollo(USA)missions.AmapoftheaverageatomicnumberofthelunarrockandsoilonthelunarsurfacehasbeenderivedfromtheGamma-RaySpectrometerdatacollectedbyChang’e-1,anunmannedChineselunar-orbitingspacecraft.Inthemap,thehigheraverageatomicnumbers(ZA>12.5),whicharerelatedtodifferenttypesofbasalt,areinthemariaregion;thehighestZA(13.2)readingsareassociatedwithSinusAestuum.ThemiddleZA(~12.1)regions,intheshapeofirregularovalrings,areinWestOceanusProcellarumandMareFrigoris,whichseemstobeconsistentwiththedistributionofpotassium,rareearthelements,andphosphorusasauniquefeatureonthelunarsurface.Theloweraverageatomicnumbers(ZA<11.5)arefoundtobecorrelatedwiththeanorthositeonthefarsideoftheMoon.