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.
HMI observations reveal a slow, north-south asymmetric polar magnetic field reversal. Cycle 24 has been weak; an even weaker Cycle 25 seems probable.