I got tired of all of the speculation floating around the minecraft forums about Aura decided to figure it out myself. Here is what I know. I'm only going to post conclusions that I have strong evidence for. I want this to be the final word, or as close as you can get without access to the source code.
Aura Draining
When you drain Vis out of the Aura, the node that you took the Vis from tries to recover by requesting Vis from nearby nodes. Vis always flows from larger nodes to smaller nodes, where "larger" and "smaller" refers to MAX aura, not CURRENT aura. A 50/800 node will empty itself out to top off a 450/500 node. Similarly, an overcharged 100/90 node will not lift a finger to help out a 1/800 node. This is all easily verifiable by donning Goggles of Revealing and watching how the Vis moves around.
If you follow the Vis trails, you will find that your node is being supported by a slightly larger node, and you might even find that that node is being supported by yet another even bigger node. If you follow the trail long enough, you will eventually find a big node at the end of the chain. This guy is too big to request Vis from other nodes. If you watch it for a while, you will notice that it slowly recovers aura in 10 point increments, even though you can't see any Vis flying into it from other nodes. What is happening is that that node is eating infused stone, turning it into dull ore and extracting 10 Vis for each conversion. This ore eating mechanic has been stated by Azanor himself and confirmed by other people:
http://www.minecraftforum.net/topic...updated-22122012/page__st__2480#entry19648284
http://www.minecraftforum.net/topic...012/page__st__1900__p__19578879#entry19578879
Eventually, the big "source" node will run out of infused ore and lose its ability to recover. This resource depletion continues along the chain until the entire region has been drained of Aura.
New Nodes
Silverwood saplings create a new pure node when they grow. This node will start with 50-100 Aura. This Aura is not free. It comes from the closest node that can support it. Moreover, the new node absorbs 1.5 times the amount that it gains. People argue about where this missing Aura goes, but I believe that it is simply lost. I'll explain why I think this later.
When two nodes merge, the new node is equal to the max aura of the largest node + 1/3 of the max aura of the smaller node. I have observed over 100 merging events and have never seen this rule violated. It's also been verified by people have have read the code.
http://www.minecraftforum.net/topic/1585216-thaumcraft-301c-updated-22122012/page__st__4760#entry20054550
You can get some wonkiness with merging because "largest node" is determined by CURRENT aura instead of MAX aura. If your larger node gets badly drained by the nascent node, it might count as being smaller if it can't recover before merging and the merging will happen "backwards." You can actually lose max aura this way.
For example, a 100/100 has a new 50/50 node appear right next to it. The new node draws 75 aura from the old one and throws the remaining 25 points away. The nodes are now 25/100 and 50/50. If they merge like that, the 50/50 will strangely be counted as the "large" node, and the resulting new node will have a max aura of 50 + 100/3 = 83, which is less than the starting capacity of 100.
The solution is to plant Silverwoods far enough away from your node that the old one has time to recover. In the above example, if the nodes merged after the old one recovered, the new node would have 100 +50/3 = 116, which is an improvement. New Silverwoods create nodes with capacities ranging from 50-100 (confirmed by both extensive testing and by code), so you can stop worrying about bad merges when your main node hits 251.
Ore Recovery
When an Aura is overcharged by 10 or more, it can discharge 10 Vis to restore a dull ore back into an Infused stone. The easiest way to see this for yourself is to go to a new, untouched node and cheat in some dull ores. Place some crystal clusters nearby and watch. The odds of any one dull ore being restored per tick appears to be very low, but if you place 3 or four stacks of dull ore, you should see the refill happen within a few minutes. The ores won't visibly revert unless you force a block update or log off, but you can easily tell when it happens because the aura level will change.
I do not believe that the overflow Aura from Silverwood growth and from merges can refill dull ores. I have made a test setup full of dull ore and have planted and merged over 50 consecutive Silverwoods without ever seeing a single recharge event. My conclusion is that the overflow is simply lost.
According to code divers, an Aura overcharged by 100 or more has a tiny chance of creating new infused ores out of ordinary smooth stone. The rate is incredibly slow and the effect may as well not exist:
http://www.minecraftforum.net/topic...updated-22122012/page__st__4080#entry19874582
Personal Conclusions:
One thing that this has taught me is that building supernodes out of Silverwood trees actually gives you less Vis to work with, not more. Both the growth and the merges are lossy processes, and those losses are born by the surrounding nodes and their corresponding ores. Even worse, your supernode will eventually become so big that it can't request Vis from its neighbors anymore. At this point, you are limited to what ores remain in your immediate vicinity. When those run out, you are done. Actually, it is usually even worse than this. If you badly depleted the surrounding nodes, once your supernode becomes bigger than them, it will immediately start emptying itself out to restore them.
The only way to create new Vis that I have confirmed is through the use of crystal clusters. This works, but is very slow (roughly one point of Aura per five minutes). Crystal clusters can overcharge your node (but never by more than 10%), which theoretically can restore your ores. Like I mentioned earlier, the per-ore odds are very low (my first test had only 9 blocks of dull ore and my overcharged node failed to refill even one of them after 24 hours of continuous running). Also, overcharged auras build up Flux very fast. You might get a few ores back, but it could days or even weeks of real life time to get the Flux back down to acceptable levels if you insist on totally refilling everything.
If you just want lots of Vis for crafting, find a small Pure node somewhere and set up there. Your total Vis will effectively be equal to the nodes+ores of all of the surrounding region. Supernodes consume huge amounts of Aura to build and cut you off from remote recharges. Only make one because you like making them, not because you think it gives you an advantage.
Aura Draining
When you drain Vis out of the Aura, the node that you took the Vis from tries to recover by requesting Vis from nearby nodes. Vis always flows from larger nodes to smaller nodes, where "larger" and "smaller" refers to MAX aura, not CURRENT aura. A 50/800 node will empty itself out to top off a 450/500 node. Similarly, an overcharged 100/90 node will not lift a finger to help out a 1/800 node. This is all easily verifiable by donning Goggles of Revealing and watching how the Vis moves around.
If you follow the Vis trails, you will find that your node is being supported by a slightly larger node, and you might even find that that node is being supported by yet another even bigger node. If you follow the trail long enough, you will eventually find a big node at the end of the chain. This guy is too big to request Vis from other nodes. If you watch it for a while, you will notice that it slowly recovers aura in 10 point increments, even though you can't see any Vis flying into it from other nodes. What is happening is that that node is eating infused stone, turning it into dull ore and extracting 10 Vis for each conversion. This ore eating mechanic has been stated by Azanor himself and confirmed by other people:
http://www.minecraftforum.net/topic...updated-22122012/page__st__2480#entry19648284
http://www.minecraftforum.net/topic...012/page__st__1900__p__19578879#entry19578879
Eventually, the big "source" node will run out of infused ore and lose its ability to recover. This resource depletion continues along the chain until the entire region has been drained of Aura.
New Nodes
Silverwood saplings create a new pure node when they grow. This node will start with 50-100 Aura. This Aura is not free. It comes from the closest node that can support it. Moreover, the new node absorbs 1.5 times the amount that it gains. People argue about where this missing Aura goes, but I believe that it is simply lost. I'll explain why I think this later.
When two nodes merge, the new node is equal to the max aura of the largest node + 1/3 of the max aura of the smaller node. I have observed over 100 merging events and have never seen this rule violated. It's also been verified by people have have read the code.
http://www.minecraftforum.net/topic/1585216-thaumcraft-301c-updated-22122012/page__st__4760#entry20054550
You can get some wonkiness with merging because "largest node" is determined by CURRENT aura instead of MAX aura. If your larger node gets badly drained by the nascent node, it might count as being smaller if it can't recover before merging and the merging will happen "backwards." You can actually lose max aura this way.
For example, a 100/100 has a new 50/50 node appear right next to it. The new node draws 75 aura from the old one and throws the remaining 25 points away. The nodes are now 25/100 and 50/50. If they merge like that, the 50/50 will strangely be counted as the "large" node, and the resulting new node will have a max aura of 50 + 100/3 = 83, which is less than the starting capacity of 100.
The solution is to plant Silverwoods far enough away from your node that the old one has time to recover. In the above example, if the nodes merged after the old one recovered, the new node would have 100 +50/3 = 116, which is an improvement. New Silverwoods create nodes with capacities ranging from 50-100 (confirmed by both extensive testing and by code), so you can stop worrying about bad merges when your main node hits 251.
Ore Recovery
When an Aura is overcharged by 10 or more, it can discharge 10 Vis to restore a dull ore back into an Infused stone. The easiest way to see this for yourself is to go to a new, untouched node and cheat in some dull ores. Place some crystal clusters nearby and watch. The odds of any one dull ore being restored per tick appears to be very low, but if you place 3 or four stacks of dull ore, you should see the refill happen within a few minutes. The ores won't visibly revert unless you force a block update or log off, but you can easily tell when it happens because the aura level will change.
I do not believe that the overflow Aura from Silverwood growth and from merges can refill dull ores. I have made a test setup full of dull ore and have planted and merged over 50 consecutive Silverwoods without ever seeing a single recharge event. My conclusion is that the overflow is simply lost.
According to code divers, an Aura overcharged by 100 or more has a tiny chance of creating new infused ores out of ordinary smooth stone. The rate is incredibly slow and the effect may as well not exist:
http://www.minecraftforum.net/topic...updated-22122012/page__st__4080#entry19874582
Personal Conclusions:
One thing that this has taught me is that building supernodes out of Silverwood trees actually gives you less Vis to work with, not more. Both the growth and the merges are lossy processes, and those losses are born by the surrounding nodes and their corresponding ores. Even worse, your supernode will eventually become so big that it can't request Vis from its neighbors anymore. At this point, you are limited to what ores remain in your immediate vicinity. When those run out, you are done. Actually, it is usually even worse than this. If you badly depleted the surrounding nodes, once your supernode becomes bigger than them, it will immediately start emptying itself out to restore them.
The only way to create new Vis that I have confirmed is through the use of crystal clusters. This works, but is very slow (roughly one point of Aura per five minutes). Crystal clusters can overcharge your node (but never by more than 10%), which theoretically can restore your ores. Like I mentioned earlier, the per-ore odds are very low (my first test had only 9 blocks of dull ore and my overcharged node failed to refill even one of them after 24 hours of continuous running). Also, overcharged auras build up Flux very fast. You might get a few ores back, but it could days or even weeks of real life time to get the Flux back down to acceptable levels if you insist on totally refilling everything.
If you just want lots of Vis for crafting, find a small Pure node somewhere and set up there. Your total Vis will effectively be equal to the nodes+ores of all of the surrounding region. Supernodes consume huge amounts of Aura to build and cut you off from remote recharges. Only make one because you like making them, not because you think it gives you an advantage.
