Tuija I. Pulkkinen Finnish Meteorological Institute Helsinki, Finland

1. Inner magnetospheric dynamics: How the solar wind and outer magnetosphere drive theradiation belts and ring current- Recent advances - Challenges Tuija I. Pulkkinen Finnish Meteorological Institute Helsinki, Finland

2. Space weather chain 1. Solar activity drives solar wind structures and dynamics 2. Solar wind interaction drives magnetospheric dynamics 3. Inner magnetosphere responds to solar wind and magnetospheric driving

3. Inner magnetosphereplasmas • Plasmasphere • 1-10 eV ions • ionospheric origin • Ring current • 50-500 keV ions • both ionospheric and solar wind origin • Outer radiation belt • 0.1-10 MeV electrons • magnetospheric origin (Goldstein et al.) (Goldstein et al.) (Reeves et al.)

4. Inner magnetospheremodels • Plasmasphere • cold ion drifts • electric field • Ring current • particle tracing • drift approximation not always valid! • Outer radiation belt • diffusion models • Mostly: no couplings! (Goldstein et al.) (Goldstein et al.) (Reeves et al.)

5. Fluid description MHD simulations solve self-consistent (single-) fluid equations Kinetic description RAM-codes solve the bounce-averaged Vlasov equation in given electromagnetic fields Empirical models magnetic field evolution from fitting empirical models to observations particle tracing in drift approximation Difficulties in modeling the inner magnetosphere coupling to ionosphere and solar wind driver important coupling of large-scale and microscale processes multiple plasma populations (cold plasmasphere, plasma sheet, ring current, radiation belts) highly varying E and B in multiple scales poor observational coverage (especially electric field) Large-scale models for inner magnetosphere

6. Space weather chain 1. Solar activity: what is the solar wind ? MHD simulations: Outer boundary: solar driving Inner boundary: inner magnetosphere boundary condition • 2. What are the • key processes ? • reconnection • energy transport 3. What are the couplings to the ionosphere and inner magnetosphere ?

7. GUMICS-4 global MHD simulation Inputs Solar wind and IMF Solar EUV proxy F10.7 Earth’s dipole field Models Ideal MHD in solar wind and magneto- sphere Electrostatic equations in ionosphere • Couplings • Mapping • to ionosphere • - precipitation • - FAC • Mapping to • magnetosphere • - potential Magnetosphere Ionosphere

8. X-line controls energy conversion and input X-line Energy conversion Energy input Change of field topology (Laitinen et al., 2006, 2007)

9. Conversion from plasma to magnetic energy X-line controls energy conversion and input X-line Energy conversion Energy input (Laitinen et al., 2006, 2007)

10. Energy flux from solar wind into magnetosphere X-line controls energy conversion and input X-line Energy conversion Energy input (Laitinen et al., 2006, 2007)

11. high P low P Both Bz and Psw control energy entry Energy entry: • driven by reconnection, (IMF Bz), modulated by pressure Psw Energy conversion: • strong B-annihilation at the nose, flux generation behind cusps Ionospheric dissipation: • driven by frontside reconnection (IMF Bz), rate controlled by Psw (Pulkkinen et al, JASTP, 2007)

12. Both Bz and Psw control energy entry Energy entry: • driven by reconnection, (IMF Bz), modulated by pressure Psw Energy conversion: • strong B-annihilation at the nose, flux generation behind cusps Ionospheric dissipation: • driven by frontside reconnection (IMF Bz), rate controlled by Psw (Pulkkinen et al, JASTP, 2007)

13. high P low P Both Bz and Psw control energy entry Energy entry: • driven by reconnection, (IMF Bz), modulated by pressure Psw Energy conversion: • strong B-annihilation at the nose, flux generation behind cusps Ionospheric dissipation: • driven by frontside reconnection (IMF Bz), rate controlled by Psw (Pulkkinen et al, JASTP, 2007)

14. Tail dynamics determined by driver • Increasing EY = V.Bz changes magnetospheric response • increasing Bz stabilizes tail • increasing V increases fluctuations and variability original run increased Bz increased V (Pulkkinen et al, GRL, 2007)

15. Conclusions from MHD simulations • Energy entry controlled by reconnection • energy input through magnetopause determines ionospheric dissipation and tail reconnection efficiency • Solar wind speed is a key controlling factor • for the same Ey: • higher V and lower IMF Bz  higher activity • lower V and higher IMF Bz  lower activity • for the same pressure Psw: • higher V and lower N  higher activity • lower V and higher N  lower activity

16. Empirical magnetic field modeling Event-oriented magnetic field models • empirical formulation of magnetospheric current systems based on Tsyganenko models • give evolution of current systems for specific events

17. magneto- pause ring current tail current What creates Dst? Early main phase: • tail current intensifies, causes Dst drop Later main phase: • ring current develops, causes Dst minimum Moderate storms: • tail current dominates Intense storms: • ring current dominates (Ganushkina et al, 2004)

18. Drift modeling of particle motion Particle motion in drift approximation • conservation of 1st and 2nd adiabatic invariants • prescribed electric and magnetic fields (test particle approach) • gives ion energy distributions in the inner magnetosphere

19. What drives inner magnetosphere fluxes? Standard case: • constant dipole B-field, Volland-Stern convection • low fluxes, low energy Empirical model case: • time-dependent B-field, convection from ionosphere (Boyle) • larger fluxes, more high-energy particles 20 - 80 keV 80 - 200 keV Dipole Empirical fields (Ganushkina et al., 2006)

20. Conclusions from empirical models • Inner magnetosphere energy density controlled by (small-scale) electric and magnetic field variations • rapid, small-scale variations lead to higher fluxes and more energization of the ring current • Accurate representation of the large-scale fields is critical for ring current evolution • B-field variations change particle orbits which leads to losses to magnetopause • B-field and E-field variations energize particles much more than adiabatic inward convection

21. Inner magnetosphereinteractions • Plasmasphere • supports low-frequency waves • Ring current • modifies magnetic field • participates in wave generation • Outer radiation belt • electrons accelerated and scattered by waves (from Reeves, after Summers et al.)

22. Inner magnetospherechallenges Pulkkinen et al. Cosmic vision call 2007 • Generation of waves • interactions between plasmas and fields • Net balance between sources and losses • identification of all processes • External driving • solar wind, magnetosphere, and ionosphere WARP Waves and Acceleration of Relativistic Particles

23. Inner magnetospherechallenges Pulkkinen et al. Cosmic vision call 2007 • Wave properties • chorus, hiss, EMIC wave amplitudes, growth rates, location • Wave-particle interactions • energy, pitch-angle diffusion • External driving • plasma sheet sources, E & B fields, diffusion rates, ionospheric outflow • solar wind coupling WARP Waves and Acceleration of Relativistic Particles