1. Tuija I. Pulkkinen Finnish Meteorological Institute Helsinki, Finland
Inner magnetospheric dynamics: How the solar wind and outer magnetosphere drive the radiation 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 magnetosphere plasmas
Plasmasphere
1-10 eV ions
ionospheric origin
Ring current
keV ions
both ionospheric and solar wind origin
Outer radiation belt
MeV electrons
magnetospheric origin
(Goldstein et al.)
(Goldstein et al.)
(Reeves et al.)

4. Inner magnetosphere models
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. Large-scale models for inner magnetosphere
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)

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
Energy input
Change of
field topology
(Laitinen et al., 2006, 2007)

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

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

11. Both Bz and Psw control 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
high P
low P
(Pulkkinen et al, JASTP, 2007)

12. Both Bz and Psw control 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. Both Bz and Psw control energy entry
high P
low P
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. What creates Dst? Early main phase:
magneto-
pause
ring
current
tail
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
keV 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 magnetosphere interactions
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 magnetosphere challenges
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 magnetosphere challenges
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