The stability of sunspots is one of the long-standing unsolved puzzles in the field of solar magnetism and the solar cycle.

Recently, there have been some reports of unusually strong photospheric magnetic fields (which can reach values of over 7 kG) inferred from Hinode SOT/SP sunspot observations within penumbral regions.

Solar magnetic activity exhibits variations with periods between 1.5–4 years, the so-called quasi-biennial oscillations (QBOs), in addition to the well-known 11-year Schwabe cycles. The solar dynamo is thought to be the responsible mechanism for the generation of the QBOs.

The Sun occasionally goes through Maunder-like extended grand minima when its magnetic activity drops considerably from the normal activity level for several decades. Many possible theories have been proposed to explain the origin of these minima.

Solomon & Qian show that solar minima are not all the same, and may have implications for understanding the Sun during the extended periods of very low activity known as “grand minima” that have sometimes occurred in the past, the best known of which was the Maunder Minimum during 1650–1700.

In 2011, three satellites—the Solar-Terrestrial RElations Observatory (STEREO) A & B, and the Solar Dynamics Observatory (SDO)—were in a unique spatial alignment that allowed a 360 degree view of the Sun. This alignment lasted until 2014, the peak of solar cycle 24.

There have been a number of reports in the literature of counter-Evershed flows in well developed sunspot penumbrae, i.e. flows directed towards the umbra.

The Sun’s outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind.