{"id":285011,"date":"2023-10-25T14:32:45","date_gmt":"2023-10-25T12:32:45","guid":{"rendered":"https:\/\/climatescience.press\/?p=285011"},"modified":"2023-10-25T14:32:49","modified_gmt":"2023-10-25T12:32:49","slug":"strange-anomaly-in-suns-solar-cycle-discovered-in-centuries-old-texts-from-korea","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=285011","title":{"rendered":"Strange anomaly in sun’s solar cycle discovered in centuries-old texts from Korea"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

The presence of grand minima, characterized by significantly reduced solar and stellar activity, brings a challenge to the understanding of solar and stellar dynamo. The Maunder Minimum (1645\u20131715 AD) is a representative grand solar minimum. The cyclic variation of solar activity, especially the cycle length during this period, is critical to understand the solar dynamo but remains unknown.<\/em><\/strong><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The sun’s solar cycles were once around three years shorter than they are today, a new analysis of centuries-old Korean chronicles reveals. This previously unknown anomaly occurred during a mysterious solar epoch known as the “Maunder Minimum,” more than 300 years ago, \u00a0 LiveScience<\/a><\/em> has the story.<\/p>\n\n\n\n

The sun<\/u><\/a> is constantly in a state of flux. Our home star cycles through periods of increased activity, known as solar maximum, when solar storms become more frequent and powerful<\/u><\/a>, as well as spells of reduced activity, known as solar minimum, when solar storms almost completely disappear.<\/p>\n\n\n\n

It currently takes about 11 years for the sun to complete a solar cycle, from minimum to maximum and back again. Scientists can track the sun’s progress through a solar cycle by counting the number of\u00a0sunspots<\/u><\/a>\u00a0on the star’s surface, which\u00a0appear more frequently in the lead-up to and during solar maximum<\/u><\/a>.<\/p>\n\n\n\n

But just as the sun fluctuates within individual cycles, historical sunspot records show that over longer periods, spanning decades or centuries, the overall output of solar cycles can also rise and fall.<\/p>\n\n\n\n

The Maunder Minimum, sometimes referred to as the Grand Solar Minimum, was a period of greatly reduced solar activity between 1645 and 1715 when sunspots “effectively disappeared,”\u00a0Scott McIntosh<\/u><\/a>, a solar physicist at the National Center for Atmospheric Research in Colorado who was not involved in the recent research, told Live Science in an email.<\/p>\n\n\n\n

\"\"
A comparison of the sun during solar maximum (left) and solar minimum (right).\u00a0(Image credit: NASA\/Solar Dynamics Observatory)<\/figcaption><\/figure>\n\n\n\n

During this time, the sun’s output was so low that average global temperatures also dropped, in what scientists have dubbed a “mini ice age,” according to NASA<\/a> \u2014 though it was also likely linked to high levels of volcanic eruptions at the time.<\/p>\n\n\n\n

Sunspot records paint a general picture of the Maunder Minimum, which is named after the English astronomer Edward Walter Maunder. But there is still much about the period that scientists don’t know. <\/p>\n\n\n\n

In the new study, published Oct. 3 in the journal\u00a0AGU Advances<\/u><\/a>, researchers analyzed historic auroral records from Korea and found that solar cycles during the Maunder Minimum were only eight years long on average \u2014 three years shorter than modern cycles.<\/p>\n\n\n\n

\"\"
This graph shows how solar activity (measured by estimated solar irradiance) dropped off during the Maunder Minimum.\u00a0(Image credit: NASA\/University of Colorado’\/LASP Interactive Solar Irradiance Datacenter)<\/figcaption><\/figure>\n\n\n\n

The aurora records were part of three separate books, or chronicles, written on behalf of Korean kings that contained detailed daily reports of royal business, state affairs, weather and astronomical phenomena that occurred within the Korean peninsula between 918 and 1910, according to the 2021 study<\/u><\/a> that first described them.<\/p>\n\n\n\n

The astronomical sections of the chronicles frequently speak of “red vapors” or “vapors like firelight.” The researchers believe these descriptions refer to the West Pacific Anomaly (WPA) \u2014 an area above Korea that produces regular red auroras despite being far from the magnetic poles. Like other auroras, the WPA occurs when solar radiation collides with Earth’s magnetic shield. But unlike other auroras at the time, these lightshows persisted despite a decrease in solar activity because the\u00a0Earth’s magnetic field<\/a>\u00a0is thinner in this region, which makes them a great proxy for solar cycle progression, the researchers wrote.\u00a0<\/p>\n\n\n\n

\"\"
A diagram of Earth showing the location of the West Pacific Anomaly (WPA).\u00a0(Image credit: Yan et al. 2023)<\/figcaption><\/figure>\n\n\n\n

The dates when these auroras occurred show that solar radiation from the sun followed an eight-year cycle.<\/p>\n\n\n\n

Scientists don’t know what causes long-term solar cycle trends like the Maunder Minimum, McIntosh said. There are “many things” that could influence solar activity over such long periods, he added. It is also unclear why the solar cycles shortened during that time. But the new findings could provide “pivotal clues” in understanding this mysterious epoch in greater detail, researchers wrote in the paper.<\/p>\n\n\n\n

Over the last few solar cycles, solar activity has decreased slightly, and there have been some slight fluctuations in cycle length. This led some experts to predict that we were entering a new epoch of reduced solar activity.<\/p>\n\n\n\n

However, the progression of the current solar cycle, which\u00a0has been very active and is fast approaching solar maximum<\/u><\/a>, suggests this is not the case.<\/p>\n\n\n\n

Read the full article\u00a0here<\/a>.<\/em><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\n\n\n\n