A Whole New Solar Cycle

What is the Solar Cycle?


This is where the sun changes from having virtually no sunspots to many, and back down again, taking a total of around 11 years to complete. However, this can range in both time (from 8 to 14 years) and peak activity.


It consists of 2 solar minimums, with low numbers of sunspots and their location at ~30º latitude north and south, and 1 solar maximum, with higher numbers of sunspots and their location around the equator (0º) [1].


The 23rd Solar Cycle

The 23rd Solar Cycle. Credit: NASA


What are Sunspots?


They can be seen as dark spots (made of a very dark “umbra” and a lighter “penumbra” around this) on the photosphere (the surface of the sun visible when using the correct filters, being a thin 100km thick compared with the Sun’s 700,000km radius [2]), at a cool 5,800 Kelvin (5526.85ºC), just cooler than the Earth’s outer core [3], having diameter of up to 50,000km (a Greece and a Fiji [4]).


It indicates interactions from the Sun’s complex and little understood magnetic field, as well as solar flares (an explosion of radiation released from the surface of a sunspot, stored in ‘twisted’ magnetic fields [5]). [6] [7]


Sunspots taken with taken by the Hinode's Solar Optical Telescope in 2006

Sunspots taken with taken by the Hinode's Solar Optical Telescope in 2006.

Credit: NASA/JAXA


Welcome to a New Age


Various agencies have now confirmed that, in December 2019, the Sun reached solar minimum, bringing about a new solar cycle (the 25th to be reliably observed, counted since 1755 [12]), and is predicted to reach a maximum between November 2024 and March 2026 (looking likely to hit 115 sunspots at its peak by July 2025, with the highest activity seeing over 200 [8]) indicating the midpoint of the solar cycle [9].


So, from hereon-in, the Sun will emit more and more radiation and will become more and more exciting to observe, if you have the right equipment to do so.


What does this solar cycle hold? Well, we can only speculate: it is widely thought that it will be similar to the previous, but it may be lower in activity than the last (with a general downward trend seen in the last 3 solar cycles), or higher, signalling the beginning of a new upwards trend in the peak number of sunspots (the measure of the Sun’s activity) [10]


Butterfly Diagram of sunspots

Butterfly Diagram of sunspots. Credit: David Hathaway, NASA, Marshall Space Flight Centre


How does it Happen?


The Sun has poles, like the Earth’s or a bar magnet’s, but with a key difference: these poles are generated inside a star, made of plasma. This makes a whole lot of difference when looking at its stability. The Earth’s poles have flipped 100 times in the past 20 million years (taking around 1,000 years to flip each time) [11]; relatively stable compared to the Sun, flipping every 11 years at solar maximum; the midpoint of the solar cycle, slowing activity down to a minimum (where we’re at now) before bringing in a new solar cycle [10].


These regular flips in the Sun’s magnetic field need to be understood by looking at how they’re generated. It’s thought that, deep inside the Sun, the electrically conducting plasma flows in such a way so as to create a ‘dynamo’ type effect, creating these magnetic fields. Indeed, when this flow weakens, the Sun’s overall magnetic field, and so its activity, weakens, creating a ‘Grand Minimum’, giving evidence for this theory of how the Sun’s magnetic fields are produced [13].


Then, during a flip, the Sun’s massive heliosphere (the spread of the Sun’s magnetic field, being billions of kilometres past Pluto; a dwarf planet 5.9 billion km from the Sun [14], and 10,000km thick) creates waves in the field (doing things such as deflecting cosmic rays) before then stabilising as it completes the process [15].


Heliosphere During a Flip

Heliosphere During a Flip. Credit: Werner Heil/NASA


Why does this Matter?


The most obvious way is with the aurorae, since they’re caused by charged particles emitted from the Sun interacting with the Earth’s magnetosphere (its version of the Sun’s heliosphere), some of which are captured at the poles and accelerated towards the atmosphere, interacting with it and producing the aurorae [16] (although there is new science all the time about this event, being one of the many topics in astronomy which we don’t yet have the whole story to). In general, they will now become more numerous and stronger, seen once or twice per month at this cycle’s maximum, but for now at least, once or twice a year (but this relatively boring time will soon be over!).


Along with this, nature will feel hard hit, in ways you might not expect. Migrating birds are a common example of animals that use an ‘internal compass’ to navigate. However, increased solar activity (as seen at solar maximum) can interfere with the signal from the Earth’s magnetic field, leading to confusion, causing significant errors in direction [17].


There are, though, far more deadly outcomes of the solar cycle, which are to be seen in the coming years. As the Sun becomes more active, it gets more likely that large solar events such as solar flares or coronal mass ejections, also known as CMEs, (events which eject light, energy and matter into the surrounding environment) occur (although they can occur at any time) [18].


They can either interfere with satellite communications by blinding the signal produced by a satellite, with a much brighter signal from solar wind [19] or even power outages as power grids are disrupted by the interference [20].


That said, it’s unlikely for that to be powerful enough to affect us on Earth, but instead the damage is mainly probable to occur in space, where instruments aren’t protected by the Earth’s magnetic field, so need much less energised solar wind (the stuff that’s ejected from the Sun) to damage the equipment [21].

Coronal Mass Ejection

Coronal Mass Ejection. Credit: NASA Earth Observatory.


Overall though, I feel this is a little bit of good news for this year, as we seek better chances of those hidden gems of aurorae further south and of capturing the Sun in its active glory (using the correct precautions of course) in the near future (something to look forward to!).


by George Abraham, ADAS member


#Sun #CME #Satellite #SolarMin #SolarCycle #Heliosphere #Plasma #MagneticField


Click here for the previous news article

Click here for the next news article


Click here to see the current solar activity, to discover if you can catch a glimpse of the aurorae or sunspots on the sun (using the correct viewing equipment), along with other widgets to tell you everything from the cloud forecast to ISS flyovers.


Click here for the ADAS guide to the cosmos, including information on the Sun

References

  1. "Solar Cycle Primer". NASA. Archived from the original on 7th November 2020.

  2. "The Photosphere". NASA Marshall Space Flight Centre. Archived from original on the 7th November 2020.

  3. "Earth's Core 100 degrees hotter than expected". Live Science. Archived from the original on 7th November 2020.

  4. "Land Area (sq. km)". The World Bank. Archived from the original on 7th November 2020.

  5. "What are Solar Flares". ESA. Archived from the original on 7th November 2020.

  6. "What are Sunspots". Space.com. Archived from the original on 7th November 2020.

  7. "What are Sunspots". SpaceWeatherLive.com. Archived from the original on 7th November 2020.

  8. "The sun has begun a new solar weather cycle. It should be pretty quiet, scientists say.". Space.com. Archived from the original on 7th November 2020.

  9. "Solar Cycle 25 has begun, say Solar Astronomers". The Sky at Night Magazine. Archived from the original on 7th November 2020.

  10. "Solar Cycle 25: The Sun Wakes Up". ESA. Archived from the original on 7th November 2020.

  11. "Earth's Magnetic Poles could start to Flip. What Happens then?". Phys.org. Archived from the original on 7th November 2020.

  12. "Solar Cycle". ESA. Archived from the original on 7th November 2020.

  13. "Why has the Sun gone Quiet?". Astronomy.com. Archived from the original on 7th November 2020.

  14. "Pluto's Distance from the Sun". Universe Today. Archived from the original on 7th November 2020.

  15. "The Sun's Magnetic Field is about to Flip". NASA. Archived from the original on 7th November 2020.

  16. "What causes the aurora borealis or 'northern lights'?". Royal Museums Greenwich. Archived from the original on 7th November 2020.

  17. "Everyday Effects of the Solar Cycle". NASA. Archived from the original on 7th November 2020.

  18. "Solar Cycle 25 is here. NASA, NOAA Scientist Explain What that Means". NASA. Archived from the original on 7th November 2020.

  19. "Sun outages: Why your TV, radio and internet might drop out in the next fortnight". ABC News. Archived from the original on 7th November 2020.

  20. "Electrical Power Transmission". NOAA. Archived from the original on 7th November 2020.

  21. "Solar Storms: Effects on Satellites". Scientific America. Archived from the original on 7th November 2020.

Recent Posts

See All
  • RSS