Storm Time Ring Current - Atmosphere Interactions: Observations and Modeling

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Rosamund Lyons
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1 Srm Time Ring Curren - Amsphere Ineracins: Observains and Mdeling V. Jrdanva 1, C. Muikis 1, L. Kisler 1, H. Masui 1, P. Puhl-Quinn 1, and Y. Khyainsev 2 (1) Space Science Cener, Universiy f New Hampshire, Durham, NH, USA (2) Swedish Insiue f Space Physics, Uppsala, Sweden Simulae he ring curren-amsphere ineracins during he large gemagneic srm f Ocber 21-25, 2001 using daa frm he MPA and SOPA insrumens n LANL spacecraf Invesigae he relaive rle f a) he cnvecin elecric field, b) radial diffusin, and c) wave-paricle ineracins n he dynamics f energeic paricles Obain H +, He +, and O + in and elecrn fluxes and sudy ring curren dawn-dusk asymmery; bain glbal images f EMIC wave grwh and in precipiain Cmpare mdel resuls wih Cluser, NOAA, and Plar bservains & Ds index Acquire knwledge needed fr he develpmen f an equarial cnvecin elecric field mdel Cluser & Duble Sar Sympsium, Sep 2005

2 Inerplaneary Observains: Ocber 21-25, 2001 An inerplaneary shck was bserved a ~16 UT n Ocber 21 IM Bz~-20 nt & slar wind speed v~700km/s; a 2 nd negaive Bz~-15 nt excursin a hur~33 Triggered a large gemagneic srm wih Ds~-190 nt; srng gemagneic aciviy lasing fr abu a day wih 2 nd minimum in Ds~-165 nt Tw enhancemens f Kp=8 - and Kp=7 + ccurred a hur~22 and hur~40

0 Re) The energy specra clearly shw he deep minimum a abu 10 kev in all species A high

3 Cluser/CODI Daa: Ocber 21, 2001 Energy specra and pich angle specra fr H +, He + and O + in he prenn secr as he S/C ges ward perigee (4.0 Re) The energy specra clearly shw he deep minimum a abu 10 kev in all species A high energies H + 90 degrees Lw energy O + and He + uflw In he inner magnesphere field aligned lw energy O + frm bh hemispheres

(a),(b) - 30-80 kev (c),(d) - 80-240 kev (e),(f) - 240-800 kev Asymmeric flux enhancemen near

4 NOAA-15 MEPED In Daa The Medium Energy Prn and Elecrn Deecr (MEPED) is an insrumen ha has been flwn n he NOAA series f plar rbiing meerlgical saellies luxes f lcally mirrring ins (a),(b) kev (c),(d) kev (e),(f) kev Asymmeric flux enhancemen near dusk during he main phase (a), (c), (e) - dawn, MLT=7 (b), (d), (f) - dusk, MLT=19 plasmapause psiin

5 ( ) ( ) and 1 where c m E γ R D R R R d d h h d de p E p d d d dr R R R R R rd am wpi cllis Cul exchange charge rd + = = = µ µ µ µ µ µ + γ γ + ϕ ϕ + + γ - relaivisic facr, m - res mass, - radial diffusin cefficiens D R R Kineic Mdel f he Terresrial Ring Curren R - radial disance in he equarial plane ϕ - azimuhal angle p - relaivisic mmenum µ =cs(α ), where α is equarial pich angle h µ ( )= 1 2 R ds 1 Bs ()B m s m s m '

6 Equarial plasmaspheric elecrn densiy In cmpsiin: 77% H +, 20% He +, 3% O + Plasmasphere Mdel: Ocber 2001

7 Inner Magnespheric Cnvecin Elecric penial in he equarial plane: Bh mdels predic srnges fields during he main phase f he srm Vlland-Sern mdel is symmeric abu dawn/dusk by definiin Weimer mdel is mre cmplex and exhibis variable eas-wes symmery and peneraes lwer L shells during acive imes

8 Cluser EDI & EW Daa and Mdel Cmparisn Elecric field in he equarial plane during he srm main phase: The fields are mapped he SM magneic equar fr each 4 s using he Tsyganenk magneic field mdel; signaures f UL (Pc5) waves are seen The slid red line indicaes 10-min running averages f he daa Weimer mdel reprduces very well he radial cmpnen bu n he azimuhal elecric field cmpnen

9 Mdel H + Cmparisn wih CLUSTER/CIS Daa Vlland-Sern mdel underesimaes he disribuin wihin he sagnain dip a lw L

10 Mdel Cmparisn wih Plar/MICS Daa: Main Phase

11 Mdel Cmparisn wih NOAA Daa H + Vlland-Sern lux H + Weimer lux NOAA/MEPED Daa Gd agreemen a 30 kev near dusk, Weimer mdel reprduces beer he iming f he enhancemen a dawn bu veresimaes he magniude

12 Self-Cnsisen Wave-Paricle Ineracins Mdel Cnvecive grwh raes f EMIC waves are self-cnsisenly calculaed using he h plasma dispersin relain: γ ω ( ) = Ψ n, E II, A Vg where n, E II, A are calculaed wih ur kineic mdel fr H +, He +, and O + ins The lcal grwh raes are inegraed alng wave pahs which are fieldaligned and exend ver ±5 magneic laiude (±10 a he plasmapause) bain he wave gain G (db) We calculae he wave ampliude B w (nt) using: B w =10x10 (G-Gmax)/Gmin fr G min <G<G max B w =10 nt fr G>G max since he ampliudes f EMIC waves reach saurain values f 10 nt in he inner magnesphere

generaed near Ds minima and during he recvery phase In precipiain is

13 EMIC Waves Exciain and In Precipiain We calculaed he wave grwh f EMIC waves frm he He + band (beween O + and He + gyrfrequency) Inense EMIC waves are generaed near Ds minima and during he recvery phase In precipiain is significanly enhanced wihin regins f EMIC wave insabiliy by wave-paricle ineracins

14 Ring Curren Energizain & Ds The Ds index is underesimaed when he Vlland-Sern cnvecin mdel is used Ring curren energizain is increased during he main phase when he Weimer mdel is used Radial diffusin enhances significanly ring curren buildup during he 2 nd Ds minimum, giving beer agreemen wih bservains

15 Cnribuin f Ring Curren Elecrns Radial diffusin injecs highenergy paricles deep in he magnesphere (L<4) and increases he al ring curren energy by ~15% near minimum Ds The elecrn cnribuin is small (~2%) during quie imes and reaches maximum values f ~10% near Ds minima

16 Cnclusins We simulaed ring curren (RC) dynamics during he large srm f Ocber 21-25, 2001 and cmpared resuls frm a) Vlland-Sern, and b) Weimer cnvecin elecric field mdels: Bh mdels reprduced he enhancemen f ~30-80 kev fluxes near dusk seen in NOAA daa; he enhancemen near dawn was underesimaed using a Vlland-Sern mdel Weimer mdel reprduced very well he radial cmpnen f he merged Cluser/EDI/EW elecric field; significan differences were seen in he azimuhal cmpnen The cmparisn wih Plar/MICS and CLUSTER/CIS in-siu daa shwed gd verall agreemen wih bh mdels; Vlland-Sern underesimaed he fluxes wihin he sagnain dip Inense EMIC waves were generaed during he main and recvery phases; his caused a significan enhancemen f he in precipiain prediced wih he mdel. Scaering by EMIC waves caused abu 10% reducin f he al RC energy Cmparisn wih Ds index shwed: -he Ds index was underesimaed when he Vlland-Sern cnvecin mdel was used; Weimer mdel reprduced faser RC buildup and beer agreemen wih bservains - radial diffusin did n affec RC buildup during he early main phase bu increased significanly he al ring curren energy during he recvery phase urher exensins f his wrk will cnsider cnsrucing an equarial cnvecin elecric field mdel f he inner magnesphere based n merged EDI and EW daa

17 Acknwledgmens Many hanks are due : M. Thmsen and G. Reeves, Ls Alams Nainal Labrary, NM Y. Miyshi, Slar-Terresrial Envirnmen Lab, Nagya Universiy, Japan J. ennell, Aerspace Crprain, Ls Angeles, CA D. Evans, SEC/NOAA, Space Envirnmen Lab, Bulder, CO This wrk is suppred in par by NASA under grans NNG05GG50G and NAG , and NS under gran ATM

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