Coronal radiation belts? H. S. Hudson Space Sciences Lab, UC Berkeley Elliot (1973) cartoon, from...
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Coronal radiation belts?H. S. Hudson
Space Sciences Lab, UC Berkeley
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Elliot (1973) cartoon, from http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/
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Thesis
• Elliot (1964) suggested the possibility of particle accumulation in mirror geometries in the solar corona
• I am exploring this possibility in the context of PFSS models now
• Large amounts of energy can probably be stored in the corona without substantial effects on the field and without externally driven current systems
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Mickey-fest, October 19 2006 3/19
Topics
• Coronal magnetic field: morphology, PFSS modeling, comparison with geomagnetic field
• Particle trapping: lifetimes, stability, signatures, effects
• Sources of particles: CRAND, low-level activity, convection
• Applications: energy storage (Elliot), CH boundaries, SEPs
• Detectability
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Mickey-fest, October 19 2006 4/19
Two RHESSI science nuggets
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http://sprg.ssl.berkeley.edu/~tohban/nuggets/
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Carl Stoermer
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G. A. Gary, Solar Phys. 203, 71 (2001)
(vA ~ 200 -1/2 km/s)
CH
Distribution of coronal plasma
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Sunspot cycle maximum Sunspot cycle minimum
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“Potential field source-surface model” (PFSS)
• Altschuler-Newkirk (1969), Schatten et al. (1969)
• Ingeniously simple theory of coronal structure
• Fictitious currents above “source surface” represent the solar wind
• T. Hoeksema PhD thesis (1984). Rss = 2.5 exactly and forever
• Model meets great success in the morphology of the solar wind and elsewhere
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Schrijver-DeRosa PFSS example
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PFSS ecliptic-plane field lines
PFSS ecliptic-plane field lines
PFSS “hairy ball” example
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Energy content of PFSS models
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Total magnetic energy vs time
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Energy vs time at solar minimum
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Third invariant time scale
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Physics of Elliot model
• Energy storage by trapped particles corresponds to a stress in the magnetic field
• This stress involves current systems closed in the corona itself and not injected through its boundary
• The particle stress is equivalent to an additional anisotropic pressure (“non-thermal pressure”) term, not normally considered in describing global equilibria
• Large energy densities may lead to ballooning instabilities?
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Populating the trapping zones
• CRAND: Cosmic Ray Albedo Neutron Decay
• CR interactions mainly (p, p), unlike Earth’s atmosphere
• Particle energy < 782 keV, but most CRAND neutrons escape from the corona before decaying
• Other mechanisms exist, but CRAND is a basic minimum source
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Conclusions
• Yes, the solar magnetic field can store particles for long times, but they may not form “belts”
• Yes, there are mechanisms to provide particles
• No, we have no idea if interesting numbers of particles are there
• There are some theoretical applications these particles could be applied to
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More topics…
• Banana orbits and 2.2 MeV late -ray emission
• Particle energization
• “Convective” effects in the corona
• PFSS particle trajectories
• PFSS mirror ratios and stability considerations
• What do CMEs do?
• Defining coronal-hole boundaries
• Electron detectability via synchrotron emission?
• Ion detectability via -ray imaging?