Hi all,
I once saw a practice about making a Sun animation without using particles. I tried it in UE4.16.1. I’m still a student learning and expecting all kinds of advice and suggestions for improvement 
Below shows the effect.
(Adding ‘not real Sun’ is to prevent if any misusage in science related things)
There are two separated Meshes: the sun sphere and a plane. No vertex animation. The quad plane performs the atmosphere. It splits the Sun from the center and is set to billboard inside the material. Below is the material snapshots for reference.
The Sun sphere:
http://res.cloudinary.com/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/v1/717033/M_SunSIm_ajkxs4.png
Three Noise nodes are used to make the basic bright area, black dots, and upper bright gas. Noise are based on local position and time to get some change overtime. To make it less consume I’m considering using noise maps instead of Noise node, but currently wondering how to deal with the uv arrangement of sphere to make the noise textures looks seamless when changing.
It is a simple solution that I rotated one texture by two different directions and speeds, and used sine function for different changing opacities.
Sometimes you can see very bright storm appear – this is controlled by a blueprint to randomly place a small storm mesh at the surface of the sun sphere, in order to make a bright storm and looks 3D.
Welcome any thoughts
PS: I’m wondering whether some material nodes are more consume than using several particles?