The giant cellular flows, obtained through tracking HMI-observed Dopplergrams, are used to estimate kinetic helicity and Reynolds stress inside the Sun, as well as differential rotation and poleward drift near the bottom of the convection zone.
A surface flux-transport dynamo model assimilation shows that the long-lasting active-region complexes, which appeared in the Sun’s southern hemisphere during Cycle 24, played a crucial role in the pole’s polarity reversal and the field strength at the cycle minimum.
Through simulations using Babcock-Leighton flux transport model, it is found that the abrupt changes on the polar field near solar minimum could be the cause of the sunspot number double peaks in the next solar cycle.
To assess the impact of active regions to the axial dipole moment, the authors isolate the contribution of individual regions for Cycles 21, 22, and 23 using a surface flux transport model, and find that although the top ~10% of contributors tend to define sudden large variations in the dipole moment, the cumulative contribution of many weaker regions cannot be ignored.
Long-term migration of the Sun’s open magnetic flux is studied, and its relation with the sunspot numbers is discussed.
Various observable, such as polar field, meridional flow, and sunspot number, are examined to identify information flow, causality, and time delay between them during solar cycles. It is expected that this analysis can provide observational constraints on solar cycle models and theories.
Super-synoptic map is constructed using SDO/HMI’s synoptic magnetic maps of each Carrington rotation, covering the period of May 2010 to December 2017. Polarity reversals can be clearly seen in the map.
The dipole moment observed by the WSO during the pre-minimum years of the last 4 solar cycles are used to establish a relation with the sunspot numbers of the following maximum years. The relation is then used to calculate the dipole moment for all the past cycles.
The HMI team has developed several Python codes that can be used to conveniently analyze its many magnetic field data products. Check it out!
Surface flux transport model suggests that the weak Cycle 24 is mainly caused by a number of bigger bipolar regions emerging at low latitudes with a “wrong” north-south orientation.