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--------------------------------- 2613 - SUNSPOTS - follow 11-year cycles ?
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- Somebody is not following the rules. Solar cycle number 24, which began in 2008, and the predictions for cycle 25, which will commence in 2020, are demonstrating anomalous behavior.
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- The sunspot maximum of cycle 24, which began almost a year late, looks to be the smallest in 100 years and the third in a trend of diminishing activity within sunspot cycles. So, cycle 25 likely could be smaller than cycle 24.
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- The leading solar polar magnetic field indicator in use for solar cycle 25 shows that the next cycle will be similar to the current one. This indicator has been accurate for the last four cycles.
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- Unfortunately, astronomers cannot accurately forecast the level of solar activity much past the next maximum. The internal process that recycles and amplifies the magnetic field still is not well understood.
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- This peculiar solar behavior raises questions for astronomers. Does the previous cycle hint at what the Sun has in store in the future? What can we expect for the next two or three solar cycles? Is Earth destined for a colder climate rather than a warmer climate?
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- Could our idea about our own spectral type G2 star’s peculiar midlife behavior need tweaking or even be flawed?
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- Cycle 24 is one of the weakest sunspot and magnetic activity cycles in more than a century. Cycle 24, and probably cycle 25, could be part of a suggested 100-year cycle that appears in the solar sunspot record known as the ‘Gleissberg Cycle“.
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- Analysis of trends and magnetic field strengths does indicate that the upcoming sunspot minimum will be very low, and cycle 25 will also be about the same or even at lower activity than the current one.
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- Without a predictive theory for the solar dynamo, the physical process that generates the Sun’s magnetic fields, it isn’t clear what we might expect for the next few cycles. Right now, the subsurface flow fields would seem to indicate that cycle 25 will be even weaker than the current cycle, with fewer than 100 spots.
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- Cycles tend to grow bigger and bigger over five to six cycles and then become smaller and smaller over the following five to six cycles. The Sun is currently in a phase of declining activity.
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- What causes solar cycles? Solar cycles hinge on the creation of the Sun’s magnetic fields. Researchers think these fields are triggered by the star’s internal differential rotation, which is the rotation of the solar atmosphere at different speeds, latitudes, and depths.
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- The Sun spins more slowly at the poles than at its equator. Twisting or turning these magnetic fields within the Sun’s photosphere may play a role in generating sunspots.
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- Astronomers believe solar magnetic fields are generated by dynamic flows of electrically conducting plasma in the Sun’s interior. This, in turn, generates electric currents that create the Sun’s active dynamo, responsible for generating magnetic fields.
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- Changes in differential rotation can weaken the solar dynamo. If the dynamo is weakened enough, it can spiral into what is known as a Grand Minimum. The best known of these was the so-called Maunder Minimum, a 70-year period of diminished solar activity from 1645 to 1715. During this time, observers often recorded no sunspots for years.
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- These days, the Sun is active, but unusual in its lack of sunspots. What could be causing this? Cycle 24 resembles cycles 14 and 15 at the start of the 20th century. What drove the preceding series of strong cycles that we refer to as the Modern Maximum, which is generally thought to have begun with cycle 15 in 1914? Without a complete theory for the solar dynamo, it’s difficult to know the actual driver for the weak sunspot cycles.
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- Throughout most of the 19th century, the number of sunspots tended to be low. But from 1930 to 1990, the Sun seemed a bit more active than usual. The solar cycle strength is a chaotic phenomenon, and there really is no way to predict it.
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- The early part of the 20th century saw many weak cycles. The cycle arises when the energy of the Sun’s internal plasma flows gets converted into magnetic energy. The Sun’s polar (north-south) magnetic fields, in turn, are built over the course of a cycle by the poleward transport of the magnetic field that emerges at the surface in active sunspot regions.
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- These north-south magnetic fields thread through the Sun’s convection zone, where differential rotation shears them out. This means the outer layers rotate faster at the equator and slower at the poles. These sheared fields become oriented east to west and become so strong that they emerge through the surface in active regions but with east-west polarities opposite to that of the previous cycle.
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- The strength of a cycle is determined by the strength of the Sun’s polar fields at the start of the 11-year solar cycle. The strength of the polar fields, in turn, is determined by the strength and number of active regions that erupted during the previous cycle.
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- As stars age, their rotation slows via a process known as magnetic braking. The Sun has likely already entered into a new, unpredicted, long-term, more quiescent phase of its evolution. This relatively quiet phase would play out over several hundred million years. As a result, the Sun’s short-term cycles will eventually disappear.
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- To test this hypothesis, we need to monitor the activity of a lot more stars that have been determined to be true analogs of our own Sun. Whether the onset of such a quiescent phase of solar-like activity has started already in the Sun is still an open question.
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- There are indications that the Sun is in a transitional phase of its magnetic dynamo activity, but one that is apt to last many millions of years. Models for the Sun’s convection zone dynamics coupled with the Sun’s current rotation rate tend to produce slower-rotating equators and faster-rotating poles.
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- But does the lack of sunspots affect climate at all?
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- During the solar cycle, the Sun’s luminosity varies by only 0.2 percent. But, solar X-ray intensity can vary by a factor of six to eight times while solar output in the far ultraviolet spectrum can vary by 20 percent over any given solar cycle.
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- If high-energy solar emissions affect Earth’s thermosphere and stratosphere via some unknown amplified feedback mechanism, this could affect the energy dynamics of Earth’s lower atmosphere, even to the extent of altering planetary circulation and inducing a small change in global temperatures.
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- Recent space missions have allowed researchers to study the connections between internal solar dynamics ,through probes of the Sun’s internal flows, and its magnetic and particulate output.
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- State-of-the-art computing power is enabling more realistic solar like physical parameters in computer simulations. The European Space Agency’s Solar Orbiter, expected to launch in 2018, would lead to more accurate sunspot cycle forecasts.
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- A dedicated mission to study the X-ray output of solar like stars at different hydrogen-burning main-sequence ages, including the Sun’s age, would also be helpful in terms of figuring out the variability of stellar magnetism over a star’s lifetime.
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- We need to understand the relative importance of certain physical parameters such as solar rotation, convection zone depth, the Sun’s effective temperature, and its age or evolutionary status.
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- The Sun’s convection zone ranges from about 124,000 miles in depth up to the photosphere, where photons are created. Which has the bigger impact on climate: solar dynamics or anthropogenic climate change?
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- Climate physicists and climate modelers have concluded that the impact of solar variations on global temperature change in the past few decades is far less than that due to anthropogenic factors. That is the effects of man and civilization.
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- Until they understand the Sun much better, solar researchers still won’t be able to definitively connect the dots between climate on terra firma and the absence or abundance of sunspots on our nearest star. We’re working on it.
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----------------------------------------- Other Reviews available about the sun:
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- 2599 - SUN - End of Humanity? The Sun is 4.6 billion years old. What happens to the Sun when it runs out of hydrogen for fusion energy? It will live another 5 billion years then its hydrogen will have mostly burned off and the core of the Sun will be solid helium. It will continue burning but it will be twice as hot. Humanity will need to have found another home.
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- 2598 - SUN - from our latest satellites? A new spacecraft is journeying to the Sun to snap the first pictures of the Sun's north and south poles. Now, we'll be able to look down on the Sun from above. The Sun plays a central role in shaping space around us. Its massive magnetic field stretches far beyond Pluto, paving a superhighway for charged solar particles known as the solar wind.
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- 2592 - SUN - This review discusses how the stars and the Sun formed the elements in the Periodic Table. You will learn how elements are identified in the stars. Discoveries are made in the stars that are later reproduced in the laboratories on Earth. Discoveries of the abundance of elements in the Sun tell astronomers about the evolution of the Universe.
- 2489 - SUN - facts you won’t believe? - The Sun is HOT but not so HOT. In fact, your body heat is hotter than the Sun. What? You’re kidding? Right? What you will learn from this review is that the Sun is not so hot but it is so big.
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- 2544 - SUN - and stars at our galactic center? The Milky Way's early life was the fastest growth period for nuclear disk at the center of our galaxy. During our galaxy's first 5 billion years, over 80% of the galaxy's stars were born, but then it dipped into a "quiescent" state, where star formation dropped away. A huge increase in activity occurred just 1 billion years ago, when approximately 5% of the center's stellar mass suddenly burst to life.
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- 2542 - SUN - our closest star.? It is an average star compared with the population of stars in our Universe. We can learn a lot about stars by studying our Sun, which is only 93,000,000 miles away. Sun light takes just 8.3 minutes to reach us from the surface of the Sun.
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- 2540 - SUN POWER - How much reaches your backyard? The fusion energy that heats my yard comes from 0.000000000115 pounds of hydrogen mass converted to energy every second. One hydrogen atom, a proton, has a mass of 1.67*10^-27 kilograms. My yard uses 31,000,000,000,000,000 hydrogen atoms every second in order to grow grass and a vegetable garden.
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- 2525 - SUN - new discoveries with the solar probe. The Parker Solar Probe launched in August 2018 and made its first solar flyby in November. Over its seven-year mission, the probe will buzz by the sun 24 times, swinging lower on each pass until it finally comes within four million miles of the sun’s surface.
- 2488 - SUN - facts you won’t believe? - The Sun is HOT but not so HOT. In fact, your body heat is hotter than the Sun. What? You’re kidding? Right? What you will learn from this review is that the Sun is not so hot but it is so big.
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- 2169 - The Universe is 13.8 billion years old. Our sun is 5 billion years old. Our sun must be a second or third generation star. It is composed of the residue of 2 or 3 earlier supernovae explosions from earlier stars that died spreading their elements all over the cosmos. The more we learn about our sun the more we will know about the other stars in the Universe.
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- 2168 - SUN - Parker Solar Probe. The mission's objectives include tracing the flow of energy that heats and accelerates the sun's corona and solar wind, determining the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind and explore mechanisms that accelerate and transport energetic particles.
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- 2165 - Why is the Sun so hot? The Sun’s surface is about 10,000 degrees Fahrenheit. But, surrounding the Sun is an atmosphere of gas known as the corona. This envelope of superheated gas is called a plasma and it measures more than 3,000,000 degrees. Astronomers are still trying to figure out how the outer layer of this star is so much hotter than what lies beneath it.
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- 1834 - That Lucky ol’ Sun got nothing to do? This review tells how the Sun gets its energy and how it compares with other stars in the Universe. And, how long will the Sun live?
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- 1720 - How do we know the age of the Sun? How do we know the age of the Sun? How fast is it “ burning” hydrogen? What does how fast it spinning have to do with this?
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- 1674 - What causes a star to evolve into a Red Giant star , like our Sun will do in another 5 billion years.
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- 1455 - Our Sun was born with a family of stars? Astronomers are trying to find them.
- 1220 - Does the Sun contain the Periodic Table?
- 533 - Why our Sun will become a variable star? A White Dwarf star.
- 383 - Could our Sun be a variable star?
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- Michael Gallegos , term paper , November 29, 2010, “ The Sun”.
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- February 11, 2020 2613
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