Sun Cycles and an Analysis of Upcoming Cycle 25

Recently, the sun has started a new cycle, which is predicted to be below average, and may point to a new trend in solar activity.

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By Christina Jiang

Humans have long postulated on the activities of the sun. The Egyptians proposed that the sun rose above and sunk below the Earth in cycles. The Aztecs named the sun Huitzilopochtli and gave him the endless cyclic task of fending off his matricidal crazed siblings in a chase across the sky, while the Greeks thought Apollo pulled the sun chariot every day and set down at dawn to mark the end of a daily cycle.

Now, of course, we understand things very differently: the sun is an unconscious ball of plasma. Unlike common historical perceptions that thought the sun was perfect, eternal, and unchanging (once the heliocentric model was introduced), the sun is actually constantly belching violent waves of radiation and fighting fiercely against gravity, which is to be its inexorable death. The processes of the sun, which were once understood as its rising and setting, have expanded into a comparatively comprehensive understanding of the mechanisms that govern and sustain it. Solar cycles are one of these phenomena.

The sun is settling into its 25th solar cycle, whose proposed maximum of solar activity will occur in the year 2025. Solar cycles are cycles of the sun reversing its north and south magnetic poles, about every 11 years (numbered from 1755). It is hard for scientists to determine specific times for such cycles, as the sun’s cycle is variable and may take months to confirm if it is in fact leaving behind its most recent minimum of solar activity.

Solar cycles are an interesting phenomenon. Astrophysicists believe that a comprehensive understanding of sunspot and sun flare activity within these cycles could greatly advance the understanding of stars and magnetohydrodynamic phenomena across the universe. Magnetohydrodynamics is nothing more than the study of the magnetic properties of electrically conductive liquids (such as electrolytes). In this case, the “liquid” in question is plasma.

As the magnetic field physically rotates to switch north and south poles during this process, solar activity can ramp up compared to the comparatively stable periods of minimum activity between the completion of each reversal of the poles. Currently, the most direct way of tracking solar cycles is through sunspots. During the onset of the solar cycle, sunspots appear in dense numbers all across the surface of the sun, mirrored roughly across the equator of the sun. As the cycle diminishes and comes to the next minimum, the sunspots migrate toward the equator and become much less dense. This can be represented by the Maunder Butterfly Diagram, which shows the trend of sunspots mirrored across the equator of the sun. Another characteristic of sun cycles is increased coronal mass ejections (CMEs), which are produced when the dynamo action that generates the fluid motions at the surface of the sun gives rise to complex magnetic structures. For reasons not entirely understood, these structures collapse and produce CMEs. During sun cycles, CMEs occur at a rate 50 times higher at maximum than the minimum.

More directly, space exploration is entirely dependent on weather within the solar system. For example, the upcoming Artemis Space Program depends heavily on predictions of space weather in order to properly shield astronauts from radiation and to protect satellite electronics. Solar cycle 25 is estimated to be similar to cycle 24, which was a cycle of below-average activity level. However, as the sun is variable, this does not rule out the possibility of extreme solar weather (as if 2020-21 needed more extreme weather).

Solar storms, accompanied by CMEs and other solar flares, can influence the Earth’s atmosphere on century (or longer) time scales. It is hard to measure the breadth of the sun’s effect on natural processes exactly, as there is a mix of factors. It would also be interesting to consider how sun cycles might affect the photosynthesizing organisms on Earth. Still, it is conclusive that the recent drastic and swift climate changes cannot be attributed to any solar activity and are likely strictly manmade.

Further, space weather can exude direct control over manmade processes. It can affect radio communications, disrupt navigation satellites, cause the aurora borealis effect (northern lights), and affect power on Earth. For example, energy utilities will receive solar forecasts to configure their power systems and plan to have support equipment in case of geomagnetic disturbances. In general, this is nothing truly detrimental to civilization. There is only one notable exception—that of the Carrington Event of 1859, in which a massive geomagnetic storm disrupted the electrical grid for extended periods and induced significant damages. Still, the sun is a surprisingly volatile factor and is surveyed constantly by NASA.

However, the most recent cycles (23, 24, and 25) have been especially benign. The upcoming cycle is predicted to be the minimum thus far of the last two centuries, and 30 to 35 percent of scientists have proposed theories that the sun may be going into a period of extended tranquility, which is good news for human civilization (and life on Earth) and even better news for space exploration, as NASA plans to land astronauts at the lunar south pole by 2024 in the Artemis Program.

Not only do sun cycles seem to be calming, but the sun itself is distinctively indistinct. Compared to other levels of stellar activity, the sun is relatively calm. This is likely a critical factor in the development of life on Earth. Indeed, study of the solar cycles may narrow our target zone for the search of extraterrestrial life.

The odd muteness of the sun has raised two major theories. The first is that the sun itself is in a lethargic state from which it will recover normal stellar activity. If this were to be true, it would raise many concerns for the future of human civilization. On the other hand, it is entirely possible that when the sun has indeed recovered normal activity, human technology will be sufficient to protect civilization from adverse effects. The second theory is that the sun is approaching the age at which its high energy period is coming to an end, on its descent to death.

Only time—and data—will tell.