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The Sun - a summer without activity

The Sun - a summer without activity (TESIS observations, August 11, 2009)

Precisely one month ago, on 11 July 2009, the last active area of the new solar cycle disappeared from the surface of the Sun. Over the 30 days following this, neither observers on Earth nor devices in space have been able to detect the emergence of any sunspots. Due to the fact that the Sun has completed a full rotation around its axis during this period, it is possible to conclude that not only are there no sunspots on the side facing Earth, but that there are no sunspots on the entire surface of the Sun. Therefore, it seems that our star has once again returned to a state of deep solar "winter", following several sparks of activity in May-June 2009. Today (12 August) marks the start of the second month of this solar inactivity.

Sunspots are not active formations in themselves but are, on the contrary, areas of lower temperature and luminosity. However, precisely these sunspots are considered the most reliable indicator of global solar activity. The reason for this is connected with their physical formation: sunspots form exclusively in areas with a strong magnetic field or, more precisely, at the base of gigantic magnetic tubes emerging from deep within the Sun as the solar cycle develops. Furthermore, the Sun's magnetic fields are impossible to measure without using special apparatus, whereas sunspots can be seen by anyone through an ordinary optical instrument with a filter to protect the eyes. Large sunspots can even be seen with the naked eye.

Due to their ease of observation, counting numbers of sunspots is the main method of measuring the level of solar activity. This method has been used uninterruptedly for around 260 years and yields the longest-standing series of daily astronomical observations. The data gathered over this period allows us to make conclusions not only about current solar activity, but also regarding the universal laws of solar activity in general. In this way the most fundamental law in modern solar physics was discovered: cyclical changes in solar activity over periods of 11 years. In all, over a 260 year period of uninterrupted observation mankind has witnessed 23 cycles. At the present time the Sun is at its solar minimum before the start of its next cycle, which will be its 24th.

The current solar minimum is one of the "deepest" ever seen over the entire 260 year observation period and a total of 3 prolonged periods with no sunspot formation have been observed. The longest of which was observed from 21 July until 10 September, 2008 (50 days). In second place is the period from 8 March until 20 April of this year which lasted 42 days. The third period of solar inactivity is unfolding now before our very eyes - starting from 12 July, 2009. To date, this period has lasted 30 days. If no sunspots appear before 2 September then the current period of inactivity will become the longest in this solar minimum and will be recording-breaking in duration.

According to data from the TESIS observatory in orbit around the Earth, at the present time there are no signs of new active areas forming on the surface of the Sun.

The TESIS observatory