Problem set 2. Due Feb 2 in class January 22, 2009 Re-derive Poynting's theorem of energy conservation in electromagnetizm @t B2 +E2 =(8 ) = (B _B + E _E)=(4 ) =r (E B)c=(4 ) E J (1) The Sun has has large scale magnetic eld (of the order of 1 Gauss). Using the resistivity coe cient due to binary collisions derived in class, estimate resistive time scale of the Sun (time scale for resistive dissipation of magnetic eld ). Compare with e-e collision rate. Solar mass is M = 2 1033 g, Solar radius is R = 7 1010 cm. Hint: use Ohm's law and Poynting's theorem, neglect E2 B2; in the Maxwell's equation curlB = (4 =c)j + @tE=c, neglect @tE=c. To estimate average Solar temperature, use p GM=R. Particle motion near neutral layer. Consider particle motion in magnetic eld which reverse direction: Bz = +B0 for y> 0 and Bz = B0 for y< 0. Find trajectory of a particle which starts at point x0 = 0 y0 = V0=!B, Vx;0 = V0, Vy;0 = 0, where !B = eB0=mc. A particle is moving at angle to magnetic eld . A pa...