It's the search request flowing into your nodes from the rest of the network.
So it's quite normal that there are very many requests: If you're a leaf these are all requests which could score a hit on one of your files, and if you're an ultrapeer these are the search results initiated by nearby nodes as well as all requests which could store a hit in your files or the files of any of your leafs.
Details:
GnuFU en - Gnufu
-> section "Network model: Intra-ultrapeer QRP"