Is The Sun About To Chillax?

A spectacular prominence along the sun's limb photographed on Monday. Prominences are large clouds of incandescent hydrogen gas held aloft by solar magnetic fields. Credit: John Chumack

You wouldn’t know it by looking at recent photos of the sun, but three lines of research indicate that solar activity has been slowing down for more than a decade. Sunspots and other magnetic activity that liven up the sun and produce auroral storms here on Earth follow an 11-year cycle. During the last maximum in 2000, spots and the solar flares they spawn were commonplace. After an unusually long minimum, our star is once again climbing out of its ‘magnetic hole’ toward the next maximum forecast for May 2013.

Despite the rise, scientists looking at trends in solar activity have noticed three significant changes in the sun’s output that could indicate an overall decline in the coming decades:

A large, new sunspot group just made its appearance along the east limb of the sun this week. This photo was taken earlier today by the Solar Dynamics Observatory. Credit: NASA

* Sunspots form when tubes of intense magnetism rise from beneath the surface and prevent the cooling solar gases from sinking back into the sun’s interior. Spots appear black because they’re several thousand degrees cooler than the surrounding regions. Matt Penn of the National Solar Observatory and colleagues used the McMath-Pierce Telescope at Kitt Peak in Arizona to measure sunspot magnetism over the past 13 years and discovered a continuous decline in field strength.

To give you a feel for magnetic strength, Earth’s magnetic field – the one that orients our compasses – measures less than 1 gauss at the planet’s surface.  Typical sunspots are in the 2,500-3,000 gauss range. Penn measured declines of 50 gauss per year. If the trend continues and sunspots’ strengths drop below 1,500 gauss, there won’t be enough magnetic energy for them to form. Hand in hand with the drop in magnetism, spots have also been getting hotter.

* Richard Altrock, manager of the Air Force’s coronal research program at Sunspot, New Mexico, used 40 years of measurements of the sun’s outer atmosphere or corona to discover that there’s less magnetic activity at the sun’s poles than in the past.

East-west moving jet streams inside the Sun migrate from the poles toward the equator during the solar cycle. At left (solar minimum) the red jet streams are located near the poles. At right (solar maximum) they have migrated close to the equator. The jet streams are believed to play an important role in generating the Sun's magnetic field and sunspots. Credit: National Solar Observatory, Air Force Research Laboratory

* Frank Hill and Rachel Howe of the National Solar Observatory at Sacramento Peak in New Mexico studied solar jet streams of magnetic energy flowing beneath the surface of the sun using helioseismology, a technique of analyzing sound waves emitted by the sun to divine its internal structure. The streams start at the poles at the beginning of cycle and work their way down to 22 degrees north and south latitudes, where they initiate a new round of solar activity.

The latest streams began their journey in 1996 but didn’t arrive at the 22 degree mark until 13 years later instead of the usual 11. This slower than normal speed is yet another indicator of depressed solar activity.

Temperature changes are shown in the northern hemisphere during the time of the Maunder Minimum. The deeper the shade of blue, the colder. Credit: Map adapted from Shindell et al., 2001, copyright AAAS 2001

All these signs point to a 2013 maximum that will be on the low side, followed by a delayed start in the next rise of solar activity around 2021. Some scientists even suspect the next cycle may not happen at all. If that’s the case, we might be in for a long, quiet spell of virtually no sunspots and flares. The last time this happened was in the latter half of the 17th century, a period of time called the Maunder Minimum. It coincided with unusually low temperatures and long winters across much of the northern hemisphere, and may have been related to a decline in sun’s ultraviolet light.

An active sun pours out more UV light. UV light acting on oxygen atoms in the upper atmosphere creates our planet’s ozone layer. Less ozone can alter the movements of those narrow, fast-moving air currents called jet streams, which in turn can redirect the paths taken by winter storms. It’s anyone’s guess whether another extended minimum might lead to global changes in weather patterns. You can read more about possible climate effects related to the Maunder Minimum HERE.

Several up sides to a solar magnetic downside would be a safer space environment for astronauts (fewer flares to worry about), less heating of the Earth’s outer atmosphere (causes it to expand and drag down orbiting satellites more quickly), and fewer threats from magnetic storms to the grids that supply our electricity. The downside: no sunspots, flares and auroras. We’ll have to wait and see, but after this last prolonged solar minimum, I’m ready for all the fun the sun can spin.

One last note. If you live in North America, you won’t be able to see today’s total lunar eclipse in the flesh, but several websites will be broadcasting it live this afternoon through about 5 p.m. Central time. Bad news is, I checked the three out I posted in yesterday’s blog and they’re clogged or not working, so please use this one out of Dubai, United Arab Emirates. The same feed is also at this YouTube link. The picture is fantastic and the moon looks awesome! Not only that but the live narration and guests add a lot to the presentation.

5 Responses

    1. astrobob

      It won’t burn out for a long, long time. Several billion years from now, it will evolve into a red giant star. Long after that it will become a white dwarf and slowly cool for billions more years.

  1. Sunny

    I am a lucky man and I have the opportunity to see the total lunar eclipse with my own eyes! Actually it is in process now. Approximately two hours ago I catched the last eluding edge of the Moon. The process takes time and I won’t see the moment when the moon is free of the shade – it’ll be too late..Anyway it’s the first watched total lunar eclipse in my life!

    1. astrobob

      That’s wonderful, Sunny. Glad you wrote to tell us. I’ve been watching it online and it looked so nice and dark red during totality. Is that how it appeared to you?

      1. Sunny

        Yes, it looked right like you described – crimson disk with dark spot in the center. Mysterious sight! By the way if you’re wondering where I am geographically – well, that is the south of Ukraine.

Comments are closed.