Magnetic flux emergence in the quiet Sun

The solar internetwork is the site of vigorous flux emergence on small spatial scales. Flux appears in supergranular cells in the form of unipolar and bipolar patches, at a rate of 120 Mx cm^-2 day^-1. Upon appearance, magnetic elements start to move toward the cell boundaries - the network. Their mean lifetime is 7 minutes, but many of them survive longer and interact with other features on their way to the network. Bipolar structures, both small-scale magnetic loops with two footpoints and clusters of opposite-polarity patches that emerge on the same area of the solar surface within a short time interval, are responsible for more than 50% of the total internetwork flux. These are the longest-lived magnetic elements. They interact with preexisting fields and produce brightenings in the chromosphere and transition region as they rise into the atmosphere. Such elements may be important contributors to chromospheric heating. The rest of the flux appears in situ as unipolar features. They tend to be smaller and have shorter lifetimes. Flux disappears from supergranular cells through transfer to the network, fading, and cancellation, at a very similar rate of 125 Mx cm^-2 day^-1. About 40% of the flux present in the internetwork ends up in the network, supplying as much flux as it contains on time scales of only 10 hours. Fading is an equally important flux loss mechanism, followed by cancellations. The flux appearance and disappearance rates are enormous. However, the fact that a significant fraction of the internetwork flux shows up as unipolar features and disappears by fading suggests that they are the result of the concentration and dispersal of background flux which is too weak to be detected above the noise level. This component is probably flux recycled from the network, rather than newly emerged flux. If so, the actual flux emergence and disappearance rates may be smaller than implied by the observations. In this talk I will review our current understanding of flux emergence processes and interactions in the quiet Sun, using long-duration, high cadence, magnetograph observations acquired by Hinode to illustrate the evolution of small-scale magnetic elements in the solar atmosphere.