Properties of flux tubes and the relation with solar irradiance variability

At the solar surface the magnetic field is bundled into discrete elements o f concentrated flux, often referred to as magnetic flux tubes, which cover only a small fraction of the solar surface. Flux tubes span a whole spectru m of sizes, ranging from sunspots to features well below the best currently obtainable spatial resolution. Whereas sunspots have been well studied, our knowledge of the true brightne ss of small-scale magnetic features is hampered by the insufficient spatial resolution of the observations. A better understanding of the thermal and magnetic properties of these small-scale features, however, is crucial fur an understanding of (climate-relevant) long-term solar irradiance variation s.