Ring-Current-Formation环电流的形成课件.ppt

1、Dynamics ofthe Radiation Belts&the Ring CurrentIoannis A.DaglisInstitute for Space ApplicationsAthensDynamics of the near-space particle radiation environmentlMain issue:mechanism(s)that can efficiently accelerate and/or transport charged particles,leading to-build-up of storm-time ring current-enha

2、nced fluxes of MeV radiation belt electrons.Dynamics of the near-space particle radiation environmentlIn both cases,the most obvious driverlthe magnetospheric substormlappears to be insufficient Dynamics of Radiation BeltslSubstorms produce electrons with energies of 10s to 100s of keV,lbut only few

3、 of MeV energies.Dynamics of Ring Currentl(Individual)Substorms inject plenty of hot ions to the inner magnetosphere,lbut not enough to lcreate/sustain lthe ring current.Dynamics of the near-space particle radiation environmentlPresumably,lthe ring current build-up and the radiation belt enhancement

4、,lbeing processes of a lhigher level of complexity,ldisplay properties not evident at the lower levelsDynamics of Radiation Belts Close association of storm-time enhancements of relativistic electron fluxes with spacecraft failure.Spacecraft operational anomalies,SAMPEX dataBaker&Daglis,2019Dynamics

5、 of Radiation BeltsEach new mission in the inner MS brings new insights(SAMPEX,CRRES)Close correlation with storms/Large dynamic range:10 to 104(Li et al.2019).Location of the peak electron flux as a function of minimum Dst moves to lower LOBrien et al.,JGR2019Dynamics of Radiation BeltsAssociation

6、of MeV electrons with ULF waves/radial diffusion Baker and Daglis,2019Dynamics of Radiation BeltsGreen and Kivelson,2019 Polar/HIST data 2019-2019Dynamics of Radiation Belts Internal/external300-500 keV 1.1-1.5 MeV300-500 keV 1.1-1.5 MeVDstKpGEOGPS1.22 MeVequatorial flux(L=4.2)MeV Electron Flux evol

7、ution after a Storm Equatorial fluxes reach max in:-2.5 days at GEO orbit-16 hours at GPS orbit Equatorial fluxes reach max in:-2 days at GEO orbit-6 days at GPS orbitT=0T=0GPS maxGPS maxGEO maxGEO maxVassiliadis et al.,JGR 2019Region P1:Slow(2-3-day)response to hi-speed streams Characteristic of GE

8、O orbit Prob.involves ULF waves Representative study:Paulikas and Blake,1979.Region P0:Rapid(1-day)response to magnetic clouds/ICMEs.Characterizes L sum of individual effects)-feature of the emergent order of higher levels of complexityFully understand and specify radiation belt variability(CRRES,Be

9、rnie Blake)Dynamics of Radiation Belts-FuturelExplain rapid acceleration of electrons to relativistic energieslIdentify loss mechanismslDevelop accurate energetic electron modelDynamics of Radiation Belts-FutureThe classical ring conceptImage courtesy Hannu Koskinen,FMIRing Current Dynamics-RC sourc

10、es(composition)/RC asymmetry-RC formation:IMF driver-RC formation:role of substormsRing Current Sources/CompositionDaglis,Magnetic Storms Monograph 2019Fig.6 of Daglis et al.JGR2019Ring current asymmetry A very asymmetric ring current distribution during the main and early recovery phases of an inte

11、nse storm Near Dst minimum O+becomes the dominant ion in agreement with previous observations of intense stormsJordanova et al.2019 Ring Current Asymmetry&Ion CompositionRing Current Dynamics-RC sources(composition)/RC asymmetry-RC formation:IMF driver-RC formation:role of substormsRing Current Form

12、ation IMF DriverEmpirical certainty:Prolonged southward IMF drives strong convection(westward Ey)and therefore storms.Large IMF Bs=intense storms.Modeling(RAM Code:Kozyra,Liemohn,et al.)Comparative study of a solar-max and a solar-min intense storms:lIMF comparable.l“Resulting”Dst different.Ring Cur

13、rent Formation IMF DriverStorm intensity defined by IMF Bs size and duration?Not exclusively!Ring Current Formation IMF DriverRing Current Dynamics-RC sources(composition)/RC asymmetry-RC formation:IMF driver-RC formation:role of substormsRing Current Formation SubstormsRole of substormsl1960s Chapm

14、an and Akasofu:storms=cumulative result of substormsl1990s McPherron,Iyemori,et al.:purely solar driven,no substorm influencel2000s Daglis,Metallinou,Fok,Ganushkina,et al.:substorms act as catalystsDaglis 2019,2019Fig.5 of Ganushkina et al.,AnnGeo2019Ganushkina et al.showed that the observed H+accel

15、eration at high energies can be reproduced in modeling studies only through substorm-style induced E pulses.Fig.10 of Ganushkina et al.,AnnGeo2019Substorm-induced transient electric fields clearly contribute to particle accelerationRing Current Formation SubstormsRing Current Formation SubstormsEffe

16、ct of recurrent(periodic)substorms on particle accelerationRing Current Formation SubstormsRing Current Formation SubstormsRing Current Formation SubstormsDynamics of Ring CurrentNot simply a superposition,but a synergy of convection,substorm-induced electric fiels and wave-particle interactions(com

17、bined effect sum of individual effects)-a feature of the emergent order of higher levels of complexityThe ring current is a very dynamic population,strongly coupling the inner magnetosphere with the ionosphere,which is an“increasingly important”source and modulatorIMF not the sole ruler:Plasma sheet

18、 density,ionospheric outflow,substorm occurrence,all have their role in storm development.Summary RCSubstorms act catalytically:they accelerate ions to high(er)energies/they preferentially accelerate O+ions,which dominate during intense storms.Storms,being phenomena of a higher level of complexity d

19、isplay properties not evident at the lower levels(substorms/convection)Summary RCDynamics ofthe Radiation Belts&the Ring CurrentEndRB models need better satellite measurements:l Particle measurements with full pitch-angle informationl Comprehensive magnetic field measurementslWave measurementslParticle measurements in inner zoneDynamics of Radiation Belts-FutureRing Current Formation IMF DriverMay 4,2019,medium energies(20-80 keV)(a)(b)(c)(d)May 4,2019,high energies(80-200 keV)(a)(b)(c)(d)