SolarWind

http://wiki.keithl.com/SolarWind

Basics of the Solar Wind

Nicole Meyer-Vernet PSULib QB529.M485 2007

• Observatoire de Paris and Centre National de la Rechereche Scientifique website

• p009 Sun: mass 1.98892e30 kg, radius 695700 km, Luminosity 3.828e26 W +/-0.1%
• p054 plasmas interact less with radiation than with plasmas

• p057 Fermi energy

  • book's "comet-like" heliosphere model obsolete

  • Imaging the Interaction of the Heliosphere with the Interstellar Medium from Saturn with Cassini

• p057 heliospheric dust grains

• p057 plasma particle collisional free path increases strongly with speed, fast particles nearly collisionless
• p064 Magnetic mirrors: particle moving towards converging/increasing field mirrors and reflects
• p066 transverse gradient produces a small transverse drift

• p069 Vlasov equation Liouville's theorem

• p080 "upstream kinetic energy converted to downstream enthalpy, high temperature

• p083 viscous forces generally much less important than inertial effects, but

  • see E. M. Purcell Life at low Reynolds number Am. J. Phys. 45, 3–11 (1977)

• p083 ions transport momentum, determining viscosity; electrons transport heat, determining thermal conductivity
• p084 Reynolds number very large for space plasmas, viscosity generally negligable
• p084 1e6 K (kelvin) solar corona heat conductivity 1e4 W/m-K "same order of magnitude as brass"

  • NO, brass approx. 150 W/m-K Silver around 430 W/m-K

• p084 conductivity low perpendicular to B, high parallel to B only if mean free path much smaller than scales of variation.

• p088 magnetic Reynolds number convection ÷ diffusion

• p090 magnetic field freezing Alfvén's theorem

• p090 plasmas in space tied to field lines, do not mix across field
• p091 magnetized plasma has
  • inertia, corresponding to bulk kinetic energy ½ρV²
  • thermal pressure, corresponding to random kinetic energy ρkT/m
  • magnetic forces, corresponding to B²/2μ₀

• p092 V = B/(μ₀ρ)½ ≡ V_A Alfvén speed

• p098 Whistler

• p101 Bohr radius (hydrogen atom minimum energy 53e-12 meters, Bohr energy 13.6eV
• p102 stripping atom (atomic number Z) of electrons requires approximately Z² × 13.6eV

• p102 Saha ionization equation

• p105 cross sections for ionization and recombination
• p106 AB⁺ + e⁻ → A + B coefficient of dissociative recombination β ~ 1e-11/√T (units?)
• p107 Charge exchange A⁺ + B → A + B⁺, for hydrogen/proton cross section is 2e-19 meters
• p110 solar wind density 5e6/m³ at 1AU, inverse square with distance
  • velocity 300 to 800 km/s, average 400 km/s, hence 2e12/m²s or 3.3e-15 kg/s
  • or 0.4 kg/s crossing area of earth disk
• p113 sun 2e30 kg, ordinary star mass 0.1 to 100 Suns, smaller is a brown dwarf or giant planet
• p122 minimum 8e55 protons, 7% of Sun
• p123 rough estimate maximum 4e58 protons, 40 solar masses, accurate estimate about 80 solar masses
• p124 graph of solar properties versus radius (scanned from book)

  • 

• p135 maximum granule size 10x scale height, approximately 1500 km
• p136 solar rotation graph, converted to time period. Below 0.7 radius, 2.3e6 seconds period

• p137 Solar magnetism models practically uncomputable, due to Sun's huge magnetic Reynolds number
• p138 naïve modelling says field decay time 30Gy, reality is a field reversal every 11 years

• 2025 Jan - field reversal soon

• ref JN Bahcall +2 2001: Solar models: Current epoch and time dependences, neutrinos, and helioseismological properties

• ref WB Hubbard +2 2002: Theory of Giant Planets paywall

• p187 Radiative loss function F(T) ≃ 1e-32 / sqrt(T) W m³

  • Book returned to PSU library, no time to dig deep

• p451 Solar parameters
  • radius 7e5 km / mass 2e30 kg / luminosity 3.84e26 W / surface gravity 272 m/s²