Proper integration time of polarization signals of internetwork regions using Sunrise/IMaX data

Distribution of magnetic elds in the quiet-Sun internetwork areas has been a ected by weak polarization (in particular Stokes Q and U) signals. To improve the signal-to-noise ratio (SNR) of the weak polarization signals, several approaches, including temporal integrations, have been proposed in the literature. In this study, we aim to investigate a proper temporal-integration time with which an optimum SNR maintained physical properties is obtained. We use magnetographs of Zeeman sensi- tive Fe i 5250:2 A line recorded by Sunrise/IMaX to determine fraction of areas with signi cant polarization signals after temporal integrations with di erent durations. We examine several thresholds for the noise level. We also perform simple numerical sim- ulations to explore the e ect of size and lifetime of the magnetic features in obtaining the proper integration time. We nd that the maximum fraction of pixels with real detectable linear polarization signals in the quiet-Sun internetwork is achieved with a maximum integration time about 8 minutes. Variation of polarization signals with integration time is strongly dependent on lifetime and size of magnetic patches. The temporal integration should be performed with great caution since in the presence of relatively long-lived magnetic features (such as network patches) SNR increases mono- tonically by increasing the integration time. This monotonic increase does not nec- essarily correspond to the internetwork areas where the linear magnetic features are relatively short-lived.