Added new symbols for drift-wave model

DDF/principles.tex

@@ -14,7 +14,7 @@
 principle implies that the starting point for code generation will often be \LaTeX \ or Markdown format
 documents from the DJF or indeed DDF.
 \item  `Do work on the mesh representation not the particles' \\
-The mesh/continuum representation is the key to any interaction
+The mesh/continuum representation is the key to any interaction.
 Allow (weighted) particles to merge or split: importance of kd-tree or octree,
 see Martin and Cambier 2016, Teunissen and Ebert 2014, particle management Sun et al 2016 , and others
 \end{enumerate}

REF/symb.tex

@@ -198,6 +198,7 @@
 $\langle \sigma v \rangle_{REC}$ & reaction rate for recombination  & $m^3 s^{-1}$ \\
 $\langle\sigma v\rangle$ & generic reaction rate  & $m^3 s^{-1}$ \\
 $L_0$ & typical lengthscale  & $m$ \\
+$L_n$ & typical lengthscale of density variation & $m$ \\
 $L_i^{N_m}(\boldsymbol{\xi})$ &  (FE Basis) Two-dimensional Lagrange polynomial through $N_m$ nodes ${\mathbf \xi}_i$ & \\
 $L_s$ & typical lengthscale along fieldline  & $m$ \\
 $L_{\|}$ & connection length of typical fieldline  & $m$ \\
@@ -278,6 +279,7 @@
 $N_s$ & number density of isotope~$s$ & $m^{-3}$ \\
 $N_T$ & number of samples in temperature used to define typically a crossection in the ADAS database~\cite{adaswebsite,openadaswebsite} & \\
 $\nu$ & plasma kinematic viscosity & $m^2 s^{-1}$ \\
+$\nu_h$ & plasma kinematic hyperviscosity & $m^4 s^{-1}$ \\
 $\nu_\alpha$ & kinematic viscosity of species~$\alpha$ & $m^2 s^{-1}$ \\
 $\nu_{cx}=K_{cx} n_n$ & charge exchange `frequency'  & $s^{-1}$ \\
 $\nu_{e0}$ & electron kinematic viscosity caused by neutrals & $m^2 s^{-1}$ \\