Sunspots Vanishing Faster than Expected

May 1, 2018: Sunspots are becoming scarce. Very scarce. So far in 2018 the sun has been blank almost 60% of the time, with whole weeks going by without sunspots. Today’s sun, shown here in an image from NASA’s Solar Dynamics Observatory, is typical of the featureless solar disk:

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The fact that sunspots are vanishing comes as no surprise. Forecasters have been saying for years that this would happen as the current solar cycle (“solar cycle 24”) comes to an end. The surprise is how fast.

“Solar cycle 24 is declining more quickly than forecast,” announced NOAA’s Space Weather Prediction Center on April 26th. This plot shows observed sunspot numbers in blue vs. the official forecast in red:

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“The smoothed, predicted sunspot number for April-May 2018 is about 15,” says NOAA. “However, the actual monthly values have been [significantly] lower.”

“Official” forecasts of the solar cycle come from NOAA’s Solar Cycle Prediction Panel–a group of experts from NOAA, NASA, the US Air Force, universities and other research organizations. They have been convening at intervals since 1989 to predict the timing and intensity of Solar Max. The problem is, no one really knows how to predict the solar cycle. The most recent iteration of the panel in 2006-2008 compared 54 different methods ranging from empirical extrapolations of historical data to cutting-edge supercomputer models of the sun’s magnetic dynamo. None fully described what is happening now.

It’s important to note that solar minimum is a normal part of the sunspot cycle. Sunspots have been disappearing (or nearly so) every ~11 years since 1843 when German astronomer Samuel Heinrich Schwabe discovered the periodic nature of solar activity. Sometimes they go away for decades, as happened during the Maunder Minimum of the 17th century.  We’ve seen it all before. Or have we….?

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Researchers are keeping a wary eye on the sun now because of what happened the last time sunspots disappeared. The solar minimum of 2008-2009 was unusually deep. The sun set Space Age records for low sunspot number, weak solar wind, and depressed solar irradiance. When the sun finally woke up a few years later, it seemed to have “solar minimum hangover.” The bounce-back Solar Max of 2012-2015 was the weakest solar maximum of the Space Age, prompting some to wonder if solar activity is entering a  phase of sustained quiet. The faster-than-expected decline of the sunspot cycle now may support that idea.

Newcomers to the field are often surprised to learn that a lot happens during solar minimum: The sun dims, albeit slightly. NASA recently launched a new sensor (TSIS-1) to the International Space Station to monitor this effect. With less extreme UV radiation coming from the sun, Earth’s upper atmosphere cools and shrinks. This allows space junk to accumulate in low Earth orbit.

neutrons_stripAbove: A neutron bubble chamber in an airplane 35,000 feet above Greenland. Spaceweather.com and the students of Earth to Sky Calculus are flying these sensors to measure aviation radiation during solar minimum. [more]

The most important change, however, may be the increase in cosmic rays. Flagging solar wind pressure during solar minimum allows cosmic rays from deep space to penetrate the inner solar system. Right now, space weather balloons and NASA spacecraft are measuring an uptick in radiation due to this effect. Cosmic rays may alter the chemistry of Earth’s upper atmosphere, trigger lightning, and seed clouds.

Air travelers are affected, too. It is well known that cosmic rays penetrate airplanes. Passengers on long commercial flights receive doses similar to dental X-rays during a single trip, while pilots have been classified as occupational radiation workers by the International Commission on Radiological Protection (ICRP). Ongoing measurements by Spaceweather.com and Earth to Sky Calculus show that dose rates at cruising altitudes of 35,000 feet are currently ~40 times greater than on the ground below, values which could increase as the solar cycle wanes.

Solar minimum is just getting started. Stay tuned for updates.

The Sun is Dimming

Dec. 15, 2017: On Friday, Dec. 15th, at the Cape Canaveral Air Force Station in Florida, SpaceX launched a new sensor to the International Space Station named TSIS-1. Its mission: to measure the dimming of the sun. As the sunspot cycle plunges toward its 11-year minimum, NASA satellites are tracking a decline in total solar irradiance (TSI). Across the entire electromagnetic spectrum, the sun’s output has dropped nearly 0.1% compared to the Solar Maximum of 2012-2014. This plot shows the TSI since 1978 as observed from nine previous satellites:


Click here for a complete explanation of this plot.

The rise and fall of the sun’s luminosity is a natural part of the solar cycle. A change of 0.1% may not sound like much, but the sun deposits a lot of energy on the Earth, approximately 1,361 watts per square meter. Summed over the globe, a 0.1% variation in this quantity exceeds all of our planet’s other energy sources (such as natural radioactivity in Earth’s core) combined. A 2013 report issued by the National Research Council (NRC), “The Effects of Solar Variability on Earth’s Climate,” spells out some of the ways the cyclic change in TSI can affect the chemistry of Earth’s upper atmosphere and possibly alter regional weather patterns, especially in the Pacific.

NASA’s current flagship satellite for measuring TSI, the Solar Radiation and Climate Experiment (SORCE), is now more than six years beyond its prime-mission lifetime. TSIS-1 will take over for SORCE, extending the record of TSI measurements with unprecedented precision. It’s five-year mission will overlap a deep Solar Minimum expected in 2019-2020. TSIS-1 will therefore be able to observe the continued decline in the sun’s luminosity followed by a rebound as the next solar cycle picks up steam. Installing and checking out TSIS-1 will take some time; the first science data are expected in Feb. 2018. Stay tuned.

Sunspots Vanish, Space Weather Continues

Jan 11, 2017: So far in 2017, the big story in space weather is sunspots–or rather, the lack thereof. The sun has been blank more than 90% of the time.  Only one very tiny spot observed for a few hours on Jan. 3rd interrupted a string of spotless days from New Years through Jan. 11th. Devoid of dark cores, yesterday’s sun is typical of the year so far:

The last time the sun produced a similar string of spotless days was May of 2010, almost 7 years ago. That was near the end of the previous deep Solar Minimum.  The current stretch is a sign that Solar Minimum is coming again. Sunspot numbers rise and fall with an ~11-year period, slowly oscillating between Solar Max and Solar Min. In 2017, the pendulum is swinging toward the bottom.

Contrary to popular belief, space weather does not stop when sunspots vanish.  Recent nights are proof: Bright auroras have been dancing around the Arctic Circle. Tom Arne Moldenaes of Groetfjord, Norway, recorded this eruption (“like green lava from a volcano,” he says) on Jan. 5th when the face of the sun was completely spotless:

The auroras were sparked by a stream of solar wind flowing from a large hole in the sun’s atmosphere. Such “coronal holes” are common during Solar Minimum.

Sunspots are an important source of space weather. They can unleash solar flares, cause radio blackouts and geomagnetic storms. However, equally interesting things happen when sunspots vanish. For instance, the extreme ultraviolet output of the sun plummets. This causes the upper atmosphere of Earth to cool and collapse. With less air “up there” to cause orbital decay, space junk accumulates around our planet.

Also during Solar Minimum, the heliosphere shrinks, bringing interstellar space closer to Earth. Galactic cosmic rays penetrate the inner solar system with relative ease. Indeed, a cosmic ray surge is already underway, with implications for astronauts and even ordinary air travelers.

Stay tuned for updates as we enter a new phase of the solar cycle.

Realtime Aurora Photo Gallery

Sunspot Cycle at Lowest Level in 5 Years

Nov. 15, 2016: The sun has looked remarkably blank lately, with few dark cores interrupting the featureless solar disk.  This is a sign that Solar Minimum is coming.  Indeed, sunspot counts have just reached their lowest level since 2011. With respect to the sunspot cycle, you are here:

The solar cycle is like a pendulum, swinging back and forth between periods of high and low sunspot number every 11 years. These data from NOAA show that the pendulum is swinging toward low sunspot numbers even faster than expected. (The red line is the forecast; black dots are actual measurements.). Given the current progression, forecasters expect the cycle to bottom out with a deep Solar Minimum in 2019-2020.

Solar Minimum is widely misunderstood.  Many people think it brings a period of dull quiet. In fact, space weather changes in interesting ways. For instance, as the extreme ultraviolet output of the sun decreases, the upper atmosphere of Earth cools and collapses. This allows space junk to accumulate around our planet. Also, the heliosphere shrinks, bringing interstellar space closer to Earth; galactic cosmic rays penetrate the inner solar system and our atmosphere with relative ease. (More on this below.) Meanwhile, geomagnetic storms and auroras will continue–caused mainly by solar wind streams instead of CMEs. Indeed, Solar Minimum is coming, but it won’t be dull.

COSMIC RAYS CONTINUE TO INTENSIFY: As the sunspot cycle declines, we expect cosmic rays to increase. Is this actually happening? The answer is “yes.” Spaceweather.com and the students of Earth to Sky Calculus have been monitoring radiation levels in the stratosphere with frequent high-altitude balloon flights over California. Here are the latest results, current as of Nov. 11, 2016:

Data show that cosmic ray levels are intensifying with an 11% increase since March 2015.

Cosmic rays are high-energy photons and subatomic particles accelerated in our direction by distant supernovas and other violent events in the Milky Way. Usually, cosmic rays are held at bay by the sun’s magnetic field, which envelops and protects all the planets in the Solar System. But the sun’s magnetic shield is weakening as the solar cycle shifts from Solar Max to Solar Minimum. As the sunspot cycle goes down, cosmic rays go up.

The sensors we send to the stratosphere measure X-rays and gamma-rays which are produced by the crash of primary cosmic rays into Earth’s atmosphere. In this way we are able to track increasing levels of radiation. The increase is expected to continue for years to come as solar activity plunges toward a deep Solar Minimum in 2019-2020.

Recently, we have expanded the scope of our measurements beyond California with launch sites in three continents: North America, South America and soon above the Arctic Circle in Europe. This Intercontinental Space Weather Balloon Network will allow us to probe the variable protection we receive from Earth’s magnetic field and atmosphere as a function of location around the globe.

The Solar Cycle is Crashing

by Dr. Tony Phillips  of Spaceweather.com

Anyone wondering why the sun has been so quiet lately? The reason may be found in the graph below. The 11-year sunspot cycle is crashing:

For the past two years, the sunspot number has been dropping as the sun transitions from Solar Max to Solar Min. Fewer sunspots means there are fewer solar flares and fewer coronal mass ejections (CMEs). As these explosions subside, we deem the sun “quiet.”

But how quiet is it, really?

A widely-held misconception is that space weather stalls and becomes uninteresting during periods of low sunspot number. In fact, by turning the solar cycle sideways, we see that Solar Minimum brings many interesting changes. For instance, the upper atmosphere of Earth collapses, allowing space junk to accumulate around our planet. The heliosphere shrinks, bringing interstellar space closer to Earth. And galactic cosmic rays penetrate the inner solar system with relative ease. Indeed, a cosmic ray surge is already underway. (Goodbye sunspots, hello deep-space radiation.)

Stay tuned for updates as the sunspot number continues to drop.