From a4b58dfa22f8d89e2e246af0b004f7a6370f373a Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Mon, 6 Jan 2025 15:26:00 +0000
Subject: [PATCH] :memo: Enhance documentation for resistive plasma heating and
 clarify references to ITER Physics Design Guidelines

---
 .../plasma_resistive_heating.md               | 26 ++++++++++++++++++-
 process/physics.py                            |  6 ++---
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/documentation/proc-pages/physics-models/plasma_current/plasma_resistive_heating.md b/documentation/proc-pages/physics-models/plasma_current/plasma_resistive_heating.md
index 8bf0d78b..fe90e0ba 100644
--- a/documentation/proc-pages/physics-models/plasma_current/plasma_resistive_heating.md
+++ b/documentation/proc-pages/physics-models/plasma_current/plasma_resistive_heating.md
@@ -1 +1,25 @@
-# Resistive Plasma Heating
\ No newline at end of file
+# Resistive Plasma Heating
+
+The ohmic component of the plasma heating is given by that from the ITER 1989 Physics Design Guidelines[^1]
+
+Using the resistive loop voltage for a reference profile of parabolic shape with:
+
+$$
+\alpha_n \approx 0.5, \alpha_T \approx 1.0,  \alpha_J \approx 1.5
+$$
+
+
+$$
+U \  [\text{V}] \approx 2.15 \times 10^{-3} Z_{\text{eff}}\langle \gamma_{\text{NC}} \rangle \frac{I_{\text{ind}}R_0}{\kappa a^2} \frac{1}{T_{10}^{1.5}}
+$$
+
+The neoclassical (avergae) resisitivity enhancement factor $\left(\langle \gamma_{\text{NC}} \rangle \right)$ is given by an empirical fit:
+
+$$
+\langle \gamma_{\text{NC}} \rangle = 4.3 -0.6A
+$$
+
+where $A$ is valid in the range of 2.5 - 4.0.
+
+
+[^1]: N.A. Uckan and ITER Physics Group, 'ITER Physics Design Guidelines: 1989',
\ No newline at end of file
diff --git a/process/physics.py b/process/physics.py
index 4cfda0e7..f852f1b8 100644
--- a/process/physics.py
+++ b/process/physics.py
@@ -2937,7 +2937,7 @@ def plasma_ohmic_heating(
         # Density weighted electron temperature in 10 keV units
         t10 = ten / 10.0
 
-        # Plasma resistance, from loop voltage calculation in IPDG89
+        # Plasma resistance, from loop voltage calculation in ITER Physics Design Guidelines: 1989
         res_plasma = (
             physics_variables.plasma_res_factor
             * 2.15e-9
@@ -2947,8 +2947,8 @@ def plasma_ohmic_heating(
         )
 
         # Neo-classical resistivity enhancement factor
-        # Taken from  N. A. Uckan et al, Fusion Technology 13 (1988) p.411.
-        # The expression is valid for aspect ratios in the range 2.5--4.
+        # Taken from ITER Physics Design Guidelines: 1989
+        # The expression is valid for aspect ratios in the range 2.5 to 4.0
         rpfac = 4.3 - 0.6 * rmajor / rminor
         res_plasma = res_plasma * rpfac