A new upward trend will be confirmed when the market doesn't move to a consecutively lower low and high.
Public Participation Phase
When informed investors entered the market during the accumulation phase, they did so with the assumption that the worst was over and a recovery lay ahead. As this starts to materialize, the new primary trend moves into what is known as the public participation phase.
During this phase, negative sentiment starts to dissipate as business conditions - marked by earnings growth and strong economic data - improve. As the good news starts to permeate the market, more and more investors move back in, sending prices higher.
This phase tends not only to be the longest lasting, but also the one with the largest price movement. It's also the phase in which most technical and trend traders start to take long positions, as the new upward primary trend has confirmed itself - a sign these participants have waited for.