Sunspots – A Qualitative Analysis by Professor Frank Ventura

This feature is based on a presentation given by Professor Frank Ventura on 11th October, 2006

It is very important to study the Sun if we want to understand the stars. After all, the sun is the closest star to Earth, so we should take advantage of its proximity to gain information about other stars.

The Sun gives out energy in a very wide range of the spectrum. It gives out a constant amount of energy and it is very active and dynamic.

Sunspots have been observed for hundreds of years by Chinese and Korean astronomers and after 1609 by telescopic observers. The main interest has been in recording the number of sunspots. In the 19th Century, the 11-year cycle was discovered. In the 20th Century, the 22-year magnetic cycle was discovered.

The sunspot numbers change during a cycle from a minimum, to a maximum and back to a minimum again. We need to ask several questions. Does sunspot quality change: (a) during a cycle? (b) from one cycle to another cycle?

When we use the term sunspot quality, we refer to the Zurich classification of sunspot types.

The Zurich Classification of Sunspot Types

Maltese observers Mr. Tony Tanti and Professor Frank Ventura made observations of sunspots and recorded their type. Numerous observations collected over several years have returned some interesting results which you can view on the following pages by means of graphical representation.

Percentage of sunspots by zurich type (1979-86)

Percentage of sunspots by zurich type (1987-91)

Comparing the different phases of Sunspot Cycles 21 and 22 we can observe the declining phase of Cycle 21 which ended in 1986 and the rising phase of Cycle 22 which started in 1991.

Trends in sunspot types A to D in sunspot cycle 22 (1987-96)
Trends in sunspot types E, F and G in sunspot cycle 22 (1987-96)
Trends in sunspot types H and J in sunspot cycle 22 (1987-96)

Sunspot Cycle 24 (2006 — 20??)

The first sunspots of Cycle 24 have been observed. It would be interesting to follow the rise and fall in the number of sunspots and observe their quality in Cycle 24. The mix of sunspot types produced may hold a clue as to what causes the sunspot cycle.

Sunspot Cycle 22 (1987 – 1996) Quality Counts and Sunspot Index