Global Hybrid Simulations of Mercury s Magnetosphere and Comparison with MESSENGER Spacecraft Observations

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1 Global Hybrid Simulations of Mrcury s Magntosphr and Comparison with MESSENGER Spaccraft Obsrvations David Schrivr, Pavl Travnick, Brian J. Andrson Maha Ashour-Abdalla, Danil N. Bakr, Mhdi Bnna Scott A. Boardsn, Robrt E. Gold, Ptr Hllingr, Gorg C. Ho Haj Korth, Stamatios M. Krimigis, Robrt L. Richard, Mnlaos Sarantos, Jams A. Slavin, Richard D. Starr Tnth Intrnational School for Spac Simulations ISSS 10 July 26, 2011

2 Scinc Goals and Approach Examin kintic aspcts of th solar wind intraction with Mrcury s magntic fild global magntosphric structur and dynamics dos Mrcury hav a radiation blt? Us upstram solar wind conditions to initializ and driv global 3D hybrid simulations Data from th MESSENGER spaccraft usd with th global hybrid simulations plac singl point masurmnts in global contxt undrstand physical procsss occurring

3 Mrcury < 5 o R M Introduction to Spac Physics, ditd by Kivlson and Russll

4 Cartoon Drawings of Mrcury s Magntosphr Bakr t al., 1987 (Marinr 1970 s) Slavin t al., 2008 (MESSENGER 2008)

5 Byond Cartoons: Global Simulations Magntohydrodynamic (MHD) 3D fluid modling on global scals dos not includ kintic ffcts Particl in cll (PIC) trats lctrons and ions slf-consistntly rquirs unralistic paramtrs (i.., m i /m, c/v t ) inhrntly noisy Hybrid includs ion kintics (fluid lctrons) us ralistic paramtrs for smallr global systms dos not includ lctron kintics

6 Simulation Tchniqus by Scal Siz Tim Scals 1-10 s MAGNETOHYDRODYNAMIC s HYBRID s PARTICLE-IN-CELL MICRO km MESO km Spatial Scals MACRO km

7 Hybrid Cod Mthodology Ion quations (full particls): Elctron quations (masslss fluid): lt m = 0 and n = n i ; us Modifid Ohm s law: Magntic fild quation: i i dt d v r = ] [ B v E v + = i i i i m q dt d E B = t B o J µ = B T k P = n P n dt d m n + = B J E u ) ( ) ( 1 o i B i o i n T k n µ η µ B B J B B E + =

8 3D Global Hybrid Simulations CAM-CL mthod [Matthws,1994;Travnick t al., 2007] Systm stup: simulation box: N x N y N z = grid spacing: ( x, y, z) = (0.4, 1, 1)Λ i [Λ i = c/ω pi ] systm siz: L x L y L z = R M Mrcury-scald magntic dipol momnt (no tilt, no offst) SW injction at +x boundary; opn all othr sids ~ 50 particls pr grid; particls absorbd at plant Not that proton gyroradius is rsolvd Examin magntosphr for 2 cass using solar wind conditions with diffrnt IMF orintation: solar wind spd: U = 4V A = 450 km/s; dnsity: n = 15 cm -3 cas 1 IMF: B = 18 nt; B x = 16.7 nt, B y = 0, B z = 6.7 nt cas 2 IMF: B = 18 nt; B x = 16.7 nt, B y = 0, B z = 6.7 nt Not larg radial IMF componnt (B x ) for both cass

9 Hybrid Simulation Dnsity Contours Noon-Midnight Mridian Z(R M ) Z(R M ) n/n sw

10 Hybrid Simulation Dnsity Contours Equatorial Plan Y(R M ) Y(R M ) n/n sw

11 MESSENGER Mission to Mrcury MESSENGER (MErcury Surfac, Spac ENvironmnt, GEochmistry, and Ranging) launchd in 2004 thr flybys: two in 2008, on in 2009 ntrd into a polar orbit around Mrcury on March 18, 2011 Rlvant instrumnts Magntomtr (MAG) Fast Imaging Plasma Spctromtr (FIPS) ions with nrgy: 50 V/q 13.5 kv/q Enrgtic Particl Spctromtr (EPS) lctrons with nrgy: 35 kv 1 MV ions with nrgy: 15 kv/q 3 MV/q X-Ray Spctromtr (XRS) lctrons with nrgy: 1 10 kv

12 MESSENGER data Global 3D hybrid simulation dnsity contours with northward orintd IMF orbit 26

13 MESSENGER Orbital Charactristics Equatorial Plan Dusk-Dawn Mridian n/n sw Orbit 26 Orbit 52 Orbit 90 orbit 90 First data availabl orbit 12 (March 24, 2011) Orbital priod ~ 12 hours Priapsis quatorial crossing ~ 1.4 R M Orbital longitudinal prcssion ~ 3 o (clockwis looking down from north) Data xamind (so far) from 3.67 (pr-dawn) to 14.9 (aftrnoon) MLT

14 1-10 kv lctrons

15 Obsrvational Summary Equatorial crossing (priapsis at ~ 1.4 R M ): magntic dprssions: 5 50 nt ions: 1 10 kv (avrag ~ 4 kv) lctrons: 1 10 kv occasionally kv, larg pitch angl for 2 vnts wavs: obliqu EMIC, ~ Ω H+, somtims ~ Ω Na+ Statistics for orbits (MLT ): prsnt 97/102 orbits (93% any indicator availabl) wakns from MLT rlativly quit solar wind conditions prvaild during intrval xamind, but IMF B x, B z wr highly variabl

16 Plasma Physics Considrations Gyroradius (gomagntic quator B = 80 nt, W = 5 kv) ρ ion (km) = (ZW) 1/2 /B H + ~ 90 km, Na + ~ 431 km, ~ 2.1 km Loss con (dipol fild with no offst) sin θ = (B q /B plant ) 1/2 ~ 30 o anisotropic loss con distribution unstabl to EMIC wavs Azimuthal particl drift (at gomagntic quator) grad B drift: v gb = 3W /qbr; radius of curvatur drift: v rc = 2W /qbr v gb + v rc ~ 25 km/s (for 5 kv particls) 1 rotation ~ 14 min (i + clockwis, countrclockwis)

17 Quasi-trappd Population Dynamics LLBL LLBL PS PS Sourcs: low latitud boundary layr (LLBL), plasma sht (PS), plant Losss: wav-particl scattring into loss con, magntopaus shadowing Stability: for northward IMF and low-modrat solar wind prssur ~ 10% of th particls can complt a full circuit around Mrcury

18 Quasi-Trappd Population Enrgtics Lowr nrgis (~ 1-10 kv) at Mrcury compard to Earth s radiation blt (~ MV) and ring currnt (~ 100 kv) NO Quasi-trappd blt YES Why lowr nrgis at Mrcury? Possibilitis includ: gyroradius cutoff (protons > 100 kv, gyroradius > 400 km) btatron acclration not as ffctiv wav-particl intraction acclration not as ffctiv rlativly quit solar wind intrval (on CME vnt on Jun 5)

19 Summary Hybrid global simulations provid undrstanding of kintic plasma procsss at Mrcury Som highlights: ion forshock du to rflction off bow shock quasi-trappd particl population around Mrcury auroral prcipitation du to pitch-angl scattring daysid and magntotail rconnction cartoon simulation

20 Futur Dirctions Global simulation studis of comparativ magntosphrs to undrstand plasma physical procsss oprating in solar systm