AnalysisFunctions.py 文件源码

def tfps(beta=0.6, ca=1., de2=0.000545, theta=0., kk=1.):
   """
      beta: Total plasma beta,
      ca: Alfven speed based on mean field, 
      de2: me/mi, 
      theta: Angle of propagation in degrees
      kk: Wavenumber of interest in units of kdi

      Output is frequencies of the roots and the phase speeds w/k
      The roots are w[0]:Fast/Whistler, w[1]:Alfven/KAW, w[2]: Slow/Cyclotron
   """
   tht = theta*pi/180.
   ct = np.cos(tht)
   st = np.sin(tht)
   tt = st/ct
   cs=np.sqrt(beta/2.)*ca
   di =1.
   caksq=np.cos(tht)**2*ca**2
   cmsq=ca**2 + cs**2

   pcs=np.zeros(4)
   D = 1 + kk**2*de2
   # Find out the root of the quadratic dispersion relation
   pcs[0] = 1.
   pcs[1] = -(ca**2/D + cs**2 + caksq*(1+kk**2*di**2/D)/D)*kk**2
   pcs[2] = caksq*kk**4*(ca**2/D + cs**2 + cs**2*(1+kk**2*di**2/D))/D
   pcs[3] = -(cs**2*kk**6*caksq**2)/D**2
   w2 = np.roots(pcs); w = np.sqrt(w2)
   speeds= w/kk
   return w,speeds