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November 13, 2018, 09:30 UTC

The Sun goes through a minimum of the solar cycle.
The growth in activity may start already in the second half of 2019.

The Sun and the Climate — the visual art image The Sun and the Climate — the visual art image


Solar activity is currently passing through the lowest point of the 11-year cycle. This is evidenced by the data of a solar surface received from space and ground-based observations, as well as from the solar flares’ monitors recording the lowest level of solar activity in the last decade.

The cyclical nature of solar activity is one of the most reliably established facts about our star, known since the mid-19th century. Initially, it was discovered by periodically increasing and decreasing number of spots on the Sun, and subsequently was confirmed by measurements of the number of flares, the speed of the solar wind and other characteristics of the Sun as a star. The changing step of these characteristics is o average 11 years, but, it also has quite wide boarders. Shorter cycles known in history, are lasting only for 9-10 years, and long ones in a period of 12-13 years. The amplitude of the cycle also changes - from extremely large, observed, say in the middle of the 20th century, to very weak ones, recorded at the junction of the 18th and 19th centuries. It is possible that there are more global changes that span entire historical eras. But for such studies there is a lack of reliable archaeological and geological information.

The second decade of the 21st century is still showing low solar activity. The solar maximum, which was reached in 2012, despite numerous apocalyptic scenarios with links to Mayan calendars, which were even reflected in the cinema (film "2012"), turned out to be one of the weakest in modern history. This provided fuel for conflicting forecasts, from fears that the Sun would fall into the new Maunder minimum (a period of extremely low activity in the second half of the 17th century, coinciding with the Little Ice Age on the Earth), and up to the opposite scenarios when the energy which couldn’t find a way out at its maximum will be released in the next one, leading to record flashes of activity.

As usual, the answer who was right can be given only with time, and it seems that it is coming gradually. According to the measurements of the solar x-ray radiation, at the moment the state of our star coincides with the patterns of the lowest point of the cycle. Indirectly, this is also evidenced by measurements of the quantity of solar flares. If in 2016 there were 286 flares of level C and above (the point from which events can affect the Earth) recorded on the Sun, and in 2017 - 223 flares; in the current 2018 only 13 flares occurred over the last 10.5 months. Besides, the last of them was registered on 6 July 2018, that is more than 4 months ago. In other words, as it appears the Sun has now sunk to the very bottom of the solar cycle and passes through its lowest point at which the trend of solar activity is breaking. At the moment, under the solar surface at a depth of about 0.5 million km, the first magnetic fields of a new cycle should begin to form, which will gradually emerge for several months from this colossal depth until they break through to the surface and launch a new flywheel of solar flares.

The usual interval between the lower point of the cycle and the beginning of the growth of solar activity - is the interval from six months to a year. The beginning of the growth of solar activity can be expected in the second half of 2019, accordingly. Then after, from the first months of observations in particular, it will be possible to draw a preliminary conclusion on how steep the activity growth curve is and which of the scenarios of the future cycle will be realized. However, since some of these scenarios suggest the beginning of a new Maunder minimum, which means the freezing of solar cycles’ mechanism for decades, first, at least, we need to wait until the Sun leaves the current minimum.


Laboratory of X-ray astronomy of the Sun, Lebedev Institute, Russia
© XRAS tesis.lebedev.ru