Observing Evolution in the Supergranular Network Length Scale During Periods of Low Solar Activity

We present the initial results of an observational study into the variation of the dominant length scale of quiet solar emission: supergranulation. The distribution of magnetic elements in the lanes that from the network affects, and reflects, the radiative energy in the plasma of the upper solar chromosphere and transition region at the magnetic network boundaries forming as a result of the relentless interaction of magnetic fields and convective motions of the Suns’ interior. We demonstrate that a net difference of ∼0.5 Mm in the supergranular emission length scale occurs when comparing observation cycle 22/23 and cycle 23/24 minima. This variation in scale is reproduced in the data sets of multiple space- and ground-based instruments and using different diagnostic measures. By means of extension, we consider the variation of the supergranular length scale over multiple solar minima by analyzing a subset of the Mount Wilson Solar Observatory Ca ii K image record. The observations and analysis presented provide a tantalizing look at solar activity in the absence of large-scale flux emergence, offering insight into times of “extreme” solar minimum and general behavior such as the phasing and cross-dependence of different components of the spectral irradiance. Given that the modulation of the supergranular scale imprints itself in variations of the Suns’ spectral irradiance, as well as in the mass and energy transport into the entire outer atmosphere, this preliminary investigation is an important step in understanding the impact of the quiet Sun on the heliospheric system