{"id":801,"date":"2020-10-07T11:16:51","date_gmt":"2020-10-07T10:16:51","guid":{"rendered":"https:\/\/pi4zlb.vrza.nl\/wp\/?p=801"},"modified":"2020-10-07T11:16:51","modified_gmt":"2020-10-07T10:16:51","slug":"welcome-to-solar-cycle-25-our-sun-enters-a-new-11-year-period","status":"publish","type":"post","link":"https:\/\/pi4zlb.vrza.nl\/wp\/2020\/10\/07\/welcome-to-solar-cycle-25-our-sun-enters-a-new-11-year-period\/","title":{"rendered":"Welcome To Solar Cycle 25; Our Sun Enters A New 11-Year Period"},"content":{"rendered":"
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Most of us perceive time as an arrow, a one-way trip into the future. And while that\u2019s true, nature has a way of interpolating circular patterns onto that linear model \u2014 day follows night, the seasons progress through the year, and generations are born, live, and die after creating the next generation to do experience the same cycles in the future.<\/p>\n

Our star, too, follows this cyclical model, and goes through observable, periodic changes that are of keen interest to solar scientists. So it was with some fanfare that they recently announced that the sun had transitioned into Solar Cycle 25. But what exactly does that mean? Does the Sun\u2019s changing face make much difference to the average person\u2019s daily life? History shows that it can, so it pays to know what we\u2019re in store for over the next couple of decades. Welcome to your primer on Solar Cycle 25.<\/p>\n

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It Goes to Eleven<\/h2>\n

For as long as scientists have had the ability to (safely) observe the Sun, they\u2019ve noticed that our star is not the perfect glowing orb it at first appears to be. Galileo was among the first to observe that the Sun was marked by small dark imperfections. Observers began to keep track of these sunspots, noting not only their variable number but the fact that they migrate across the Sun\u2019s surface with time.<\/p>\n

It would take almost two and a half centuries for anyone to notice that the periodic nature of the patterns of sunspots. German scientist Samuel Heinrich Schwabe is credited with the discovery of the solar cycle in 1843 after 17 years of observations of the average number of sunspots. Swiss scientists Rudolf Wolf used the observations of Schwabe and others to backtrack through the data back to 1755. For solar science purposes, this was designated the year that Solar Cycle 1 started.<\/p>\n

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Cycles of sunspots for the last 400 years. The earliest data is estimated from geological and tree-ring records. By Robert A. Rohde, CC BY-SA 3.0<\/a><\/figcaption><\/figure>\n

The cycle these pioneering solar scientists had discovered has a remarkably regular eleven-year period. The range of variation is very tight, from the nine-year period of Solar Cycle 2 (1766 to 1775) to almost fourteen years for Solar Cycle 4 (1784 to 1798). Each solar cycle is reckoned from a solar minimum, essentially when the sunspot number reaches its local low. The number of sunspots increases over the first half of the cycle, peaking at the solar maximum point before turning down again to head for the next solar minimum.<\/p>\n

The raw number of sunspots is not the only interesting cycle the Sun displays. The distribution of sunspots across the Sun\u2019s surface also changes periodically with the solar cycle. At the beginning of each solar cycle, what few sunspots there are tend to cluster at the Sun\u2019s equator. As the cycle progresses and the Sun becomes more active, the sunspots tend to pop up further away from the equator, generally clustering around the mid-latitudes around 30\u00b0 north and south. As solar maximum passes, sunspots again migrate back to the equator to start the cycle again.<\/p>\n

Flipping Magnetic Poles<\/h2>\n

The periodic changes in the number and distribution of sunspots may be an interesting observation, but what does it mean here on Earth? To help understand that, it pays to recall that despite their dark appearance, sunspots are only marginally cooler than the surrounding solar material. Sunspots are still extremely energetic areas, and as the number of sunspots increases, the output of the Sun (in terms of luminosity) increases.<\/p>\n

Sunspots represent places where concentrated lines of magnetic force emerge from deep within the Sun\u2019s interior. Thus a change in the number and location of sunspots reveals changes in the magnetic field of the Sun. It turns out that what\u2019s behind the solar cycle is these periodic changes in the Sun\u2019s magnetic field. (It\u2019s important to note here that the eleven-year cycle is technically the \u201csunspot cycle,\u201d and the 22-year pole-flipping cycle is the true \u201csolar cycle,\u201d but it\u2019s common practice to use \u201cSolar Cycle\u201d for both.)<\/p>\n

The magnetic poles of the Sun are constantly in motion, with the north and south poles flipping every eleven years. At solar minimum, the magnetic poles are roughly aligned with the Sun\u2019s orbital axis, and magnetic lines of force tend to penetrate the photosphere near the equator. As the poles rotate towards the equator, magnetic activity picks up, magnetic lines of force move to high latitudes, increasing the number of sunspots there. The process continues for the back half of the solar cycle as the poles complete their reversal.<\/p>\n