2020 AGU Roundtable: What will we learn from Solar Cycle 25?

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The Solar Cycle 25 forecast, produced by the Solar Cycle 25 Prediction Panel, which is co-chaired by NASA and NOAA. Sunspot number is an indicator of solar cycle strength: the higher the sunspot number, the stronger the cycle. The panel predicts that Solar Cycle 25 will be average in intensity and similar to Cycle 24. Solar Cycle 25 is expected to peak in July 2025.

Credit: NOAA’s Space Weather Prediction Center

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This series shows how the Sun’s magnetic field evolved over the course of Solar Cycle 24. Blue represents the negative field, and yellow represents positive. The magnetic field is quiet and calm during solar minimum (2008). The magnetic field grows increasingly active and stronger, peaking during solar maximum (2014), before settling again into minimum.

Credit: Lisa Upton - www.solarcyclescience.com

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The poles are a herald of change. Just as Earth scientists watch our planet's polar regions for signs of climate change, solar physicists do the same thing for the Sun. This video shows a model of the magnetic field at the Sun’s north pole.

There are only a few observatories in the world that monitor the Sun’s polar magnetic fields. In Feb. 2020, NASA and ESA launched Solar Orbiter that will capture the first images of the Sun’s poles.

Credit: Lisa Upton - www.solarcyclescience.com

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The solar cycle is complicated. The Sun’s north and south poles aren’t in sync. A graph of Solar Cycle 24 shows how this asymmetry led to two peaks at the height of the cycle. The northern hemisphere peaked first, then the southern.

The polar magnetic field is an important measurement for solar cycle predictions. The idea is that the magnetic field at the Sun’s poles acts like a seed for the next cycle. If it’s strong during solar minimum, the next solar cycle will be strong; if it’s diminished, the next cycle should be too.

Credit: Lisa Upton

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The visible surface of the Sun as measured with an HMI visible light image from November 29, 2020. Active regions 12785 and 12786, where the flares occurred, are labeled in the southern hemisphere of the Sun. These active regions contain the sunspots.

Courtesy of NASA, SDO, and the SDO Science Teams.

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An illustration of the satellites orbiting the Earth in low-Earth orbits, within 2,000 km of the Earth's surface. It has the most concentrated density of satellites and orbital debris.

Credit: NASA Orbital Debris Program Office.

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An illustration summarizing 400 years of sunspot observations. This shows the annual average of the sunspot number since the first sunspot drawings and ends last year. Much of the data before 1800 is sporadic or incomplete, but good to excellent data is available for about 200 years.

Data courtesy of the SIDC, Brussels, Belgium and W. Dean Pesnell.

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An illustration of the numbered Solar Cycles, starting with Solar Cycle 1 in 1755. We are now in the beginning of Solar Cycle 25. The time dependence of the sunspot number shows us that solar activity rarely repeats and must be studied with data from the past and the present.

Data courtesy of the SIDC, Brussels, Belgium and W. Dean Pesnell.

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HMI visible light image from November 29, 2020.

Courtesy of NASA, SDO, and the SDO Science Teams.

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An image of the solar magnetic field measured by HMI on November 29, 2020. Outwardly directed magnetic field is in white while inwardly directed field is in black. Regions of weak magnetic field strength are grey.

Courtesy of NASA, SDO, and the SDO Science Teams.

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This is a sunspot captured by NASA’s Solar Dynamics Observatory over 24 hours on Nov. 29, 2020. The top image is a magnetogram, which shows the positive and negative charge of the sunspot groups. The bottom image shows the sunspot in a broad range of visible light.

Sunspots are a visible tracker of the solar cycle. At the Sun’s most active phase of the cycle — known as solar maximum — we will see the highest number of sunspots. At solar minimum, the calmest phase, there are little to no sunspots.

Courtesy of NASA, SDO, and the SDO Science Teams.

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A movie showing the variation of the SDO AIA 193 Å passband on November 29, 2020. This wavelength of light is in the extreme ultraviolet part of the spectrum. It is emitted by plasma at a temperature of about 2 million K.

Courtesy of NASA, SDO, and the SDO Science Teams.

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NASA’s fleet of heliophysics missions studies the Sun, its effects on Earth and the solar system and the nature of space itself.

Credit: NASA

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A movie showing the variation of the SDO AIA 304 Å passband on November 29, 2020. This wavelength of light is in the extreme ultraviolet part of the spectrum. It is emitted by plasma at a temperature of about 80,000 K.

Courtesy of NASA, SDO, and the SDO Science Teams.

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The predictions of Solar Cycle 24, organized by prediction type and in order of increasing predicted cycle strength (as indicated by sunspot number).

Credit: Dean Pesnell

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The predictions of Solar Cycle 25, organized by prediction type and in order of increasing predicted cycle strength (as indicated by sunspot number). While predictions for Solar Cycle 24 varied greatly, predictions for the current solar cycle seem to be more in agreement.

Credit: Dean Pesnell

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This is a magnetohydrodynamical simulation of the Sun’s dynamo computed using EULAG-MHD. It is widely believed that the Sun’s dynamo drives the solar cycle, but scientists are still unsure on how the dynamo exactly works. The goal of using model simulations is to replicate what is happening inside the Sun so scientists can better predict and understand its behavior.

Credit: Simulation from Strugarek et al. 2017, Science, 357, 185; Animation credits: A. Strugarek, CEA/Saclay (France)

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This is a simplified 3D dynamo simulation of the solar dynamo, covering approximately one solar activity cycle. It shows the emergence and decay of magnetic active regions at low solar latitudes, and the resulting reversal of the solar polar magnetic field. Such simulations can be used to predict the characteristics of upcoming solar cycles.

Credit: Simulation from Karak & Miesch. 2017, Astrophysical Journal, 847, 69; Animation credits: B.B. Karak, Indian Institute of Technology (India) and M. Miesch, NCAR (U.S.A.)