Archive for the ‘Solar physics’ Category

Solar Cycle Update

Posted: July 15, 2020 by oldbrew in Cycles, Solar physics
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SC 25 – are we nearly there yet?

Spaceweather.com

July 14, 2020: NOAA has released a new interactive tool to explore the solar cycle. It lets you scroll back through time, comparing sunspot counts now to peaks and valleys of the past. One thing is clear. Solar Minimum is here, and it’s one of the deepest in a century.

progression

Solar Minimum is a natural part of the solar cycle. Every ~11 years, the sun transitions from high to low activity and back again. Solar Maximum. Solar Minimum. Repeat. The cycle was discovered in 1843 by Samuel Heinrich Schwabe, who noticed the pattern after counting sunspots for 17 years. We are now exiting Solar Cycle 24 and entering Solar Cycle 25.

During Solar Minimum, the sun is usually blank–that is, without sunspots. The solar disk often looks like a big orange billiard ball:

hmi1898 The spotless sun on July 13, 2020

In 2019, the sun went 281 days without sunspots, and…

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Ionized gas inside the Sun moves toward the poles near the surface and toward the equator at the base of the convection zone (at a depth of 200,000 km/125,000 miles).
Credit: MPS (Z.-C. Liang)


The title of the study cited in this report gives us the clue: ‘Meridional flow in the Sun’s convection zone is a single cell in each hemisphere’. The full cycle takes about 22 years on average, with a magnetic reversal halfway through.
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The sun’s magnetic activity follows an 11-year cycle. Over the course of a solar cycle, the sun’s magnetic activity comes and goes, says Phys.org.

During solar maximum, large sunspots and active regions appear on the sun’s surface. Spectacular loops of hot plasma stretch throughout the sun’s atmosphere and eruptions of particles and radiation shoot into interplanetary space.

During solar minimum, the sun calms down considerably. A striking regularity appears in the so-called butterfly diagram, which describes the position of sunspots in a time-latitude plot.

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From looking at the 30 day Wolf number and NOAA sunspot number it looks like Solar Minimum could have been in December, 2019 but possibly as late as mid-March this year. 

 Coincidentally, there are peaks in barycentric solar torque (dL/dt, where L denotes the Sun’s angular momentum, ref https://arxiv.org/abs/1610.03553v3) on March 19 and April 24, 2020: 

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Sunspots [image credit: NASA]


The researchers’ sun clock looks like this.
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Extreme space weather events can significantly impact systems such as satellites, communications systems, power distribution and aviation, says a Warwick University press release.

They are driven by solar activity which is known to have an irregular but roughly 11 year cycle.

By devising a new, regular ‘sun clock’, researchers have found that the switch on and off of periods of high solar activity is quite sharp, and are able to determine the switch on/off times.

Their analysis shows that whilst extreme events can happen at any time, they are much less likely to occur in the quiet interval.

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Browsing twitter recently I ran across this short video of a solar flare shot a few days ago.

After asking for some clarification on frame rate I was really intrigued.

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Solar system [credit: BBC]

This new paper from our good friend Nicola Scafetta takes another look at the Sun’s cyclic behaviour and possible planetary influences on it, referencing various researchers whose work has appeared at the talkshop, along the way.
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Abstract
Gravitational planetary lensing of slow-moving matter streaming towards the Sun was suggested to explain puzzling solar-flare occurrences and other unexplained solar-emission phenomena (Bertolucci et al. in Phys. Dark Universe 17, 13, 2017). If it is actually so, the effect of gravitational lensing of this stream by heavy planets (Jupiter, Saturn, Uranus and Neptune) could be manifested in solar activity changes on longer time scales too where solar records present specific oscillations known in the literature as the cycles of Bray–Hallstatt (2100–2500 yr), Eddy (800–1200 yr), Suess–de Vries (200–250 yr), Jose (155–185 yr), Gleissberg (80–100 year), the 55–65 yr spectral cluster and others. It is herein hypothesized that these oscillations emerge from specific periodic planetary orbital configurations that generate particular waves in the force-fields of the heliosphere which could be able to synchronize solar activity.

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The linked article contains more video material and images.
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In February 2020, NASA’s Solar Dynamics Observatory—SDO—is celebrating its 10th year in space, reports Phys.org.

Over the past decade the spacecraft has kept a constant eye on the sun, studying how the sun creates solar activity and drives space weather—the dynamic conditions in space that impact the entire solar system, including Earth.

Since its launch on Feb. 11, 2010, SDO has collected millions of scientific images of our nearest star, giving scientists new insights into its workings.

SDO’s measurements of the sun—from the interior to the atmosphere, magnetic field, and energy output—have greatly contributed to our understanding of our closest star.

SDO’s images have also become iconic—if you’ve ever seen a close up of activity on the sun, it was likely from an SDO image.

SDO’s long career in space has allowed it to witness nearly an entire solar cycle—the sun’s 11-year cycle of activity.

Here are a few highlights of SDO’s accomplishments over the years.

A Coronal Mass Ejection with the surrounding cloud visible (1999) [image credit: NASA/ESA]


Even non-catastrophic solar storms can be troublesome, such as one in 1967 which nearly triggered nuclear war, according to evidence from retired U.S. Air Force personnel.
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A ‘great’ space weather super-storm large enough to cause significant disruption to our electronic and networked systems occurred on average once in every 25 years, according to a new joint study by the University of Warwick and the British Antarctic Survey.

By analysing magnetic field records at opposite ends of the Earth (UK and Australia), scientists have been able to detect super-storms going back over the last 150 years, reports Phys.org.

This result was made possible by a new way of analysing historical data, pioneered by the University of Warwick, from the last 14 solar cycles, way before the space age began in 1957, instead of the last five solar cycles currently used.

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Here we learn that the solar wind ‘has a sort of internal heater’, which may be short on scientific explanation but sounds interesting as far as it goes.
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There’s a wind that emanates from the sun, and it blows not like a soft whistle but like a hurricane’s scream, says Phys.org.

Made of electrons, protons, and heavier ions, the solar wind courses through the solar system at roughly 1 million miles per hour, barreling over everything in its path.

Yet through the wind’s roar, NASA’s Parker Solar Probe can hear small chirps, squeaks, and rustles that hint at the origins of this mysterious and ever-present wind.

Now, the team at the Johns Hopkins Applied Physics Laboratory, which designed, built, and manages the Parker Solar Probe for NASA, is getting their first chance to hear those sounds, too.

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Volcanic eruption


How good is the evidence for such a connection, and what theories do we have? Does a really low solar minimum – like now – make a difference? Here’s PW’s overview of its article.

Over the long term, the sun is the main driver of weather and climate on Earth and it is also directly connected to such phenomenon as the aurora borealis also known as the northern lights, upper atmospheric “high-latitude blocking”, and the influx of cosmic rays into Earth’s atmosphere, says Perspecta Weather.

The aurora borealis tends to occur more often during times of increased solar activity though they can actually take place at any time of a solar cycle.

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Contributor Steve Brown has sent me this nice plot he’s made of Solar Cycle 25 forecasts. It’s worth noting that Rick Salvador’s (blue) is the earliest, made back in 2013. The ‘NASA consensus’ forecast (green) is quite similar to Leif Svalgaard’s.

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Sunspots set a Space Age Record

Posted: December 20, 2019 by oldbrew in Solar physics
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The switch to solar cycle 25 must be getting close, if not here already.

Spaceweather.com

Dec. 17, 2019: Solar Minimum is becoming very deep indeed. Over the weekend, the sun set a Space Age record for spotlessness. So far in 2019, the sun has been without sunspots for more than 271 days, including the last 34 days in a row. Since the Space Age began, no other year has had this many blank suns.

Above: The blank sun on Dec. 16, 2019. Credit: NASA/Solar Dynamics Observatory

The previous record-holder was the year 2008, when the sun was blank for 268 days. That was during the epic Solar Minimum of 2008-2009, formerly the deepest of the Space Age. Now 2019 has moved into first place.

Solar Minimum is a normal part of the 11-year sunspot cycle. The past two (2008-2009 and 2018-2019) have been long and deep, making them “century-class” Minima. To find a year with more blank suns, you have to go back to…

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The question then is: how much life will it come to, compared to recent cycles?
Cycle 25 observations in SDO HMI imagery (to October 31st, 2019)

Spaceweather.com

Nov. 1, 2019: Breaking a string of 28 spotless days, a new sunspot (AR2750) is emerging in the sun’s southern hemisphere–and it’s a member of the next solar cycle. A picture of the sunspot is inset in this magnetic map of the sun’s surface from NASA’s Solar Dynamics Observatory:

newspot_crop2

How do we know AR2750 belongs to the next solar cycle? Its magnetic polarity tells us so. Southern sunspots from old Solar Cycle 24 have a -/+ polarity. This sunspot is the opposite: +/-. According to Hale’s Law, sunspots switch polarities from one solar cycle to the next. AR2750 is therefore a member of Solar Cycle 25.

Shortlived sunspots belonging to Solar Cycle 25 have already been reported on Dec. 20, 2016; April 8, 2018; Nov. 17, 2018; May 28, 2019; July 1, 2019; and July 8, 2019. The one on July 8, 2019, was significant because it lasted long…

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A Summer without Sunspots

Posted: September 28, 2019 by oldbrew in Solar physics
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Solar cycle 24 – going, going…

Spaceweather.com

Sept. 23, 2019: Could northern summer 2019 go down in history as “the summer without sunspots”? From June 21st until Sept 22nd, the sun was blank more than 89% of the time. During the entire season only 6 tiny sunspots briefly appeared, often fading so quickly that readers would complain to Spaceweather.com, “you’ve labeled a sunspot that doesn’t exist!” (No, it just disappeared.) Not a single significant solar flare was detected during this period of extreme quiet.

The sun on Sept. 22, 2019–as blank as a billiard ball. Credit: NASA/SDO

This is a sign that Solar Minimum is underway and probably near its deepest point. For 2019 overall (January through September), the sun has been blank 72% of the time, comparable to annual averages during the century-class Solar Minimum of 2008 (73%) and 2009 (71%). The current Solar Minimum appears to be century-class as well, meaning you have to go…

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Sunspots [image credit: NASA]


Here it’s claimed that the model matches the observations, which is surely a good start in any research. With a deep solar minimum now in progress, theorists should have plenty of new data to work with.

For 400 years people have tracked sunspots, the dark patches that appear for weeks at a time on the sun’s surface, says Phys.org.

They have observed but been unable to explain why the number of spots peaks every 11 years.

A University of Washington study published this month in the journal Physics of Plasmas proposes a model of plasma motion that would explain the 11-year sunspot cycle and several other previously mysterious properties of the sun.

“Our model is completely different from a normal picture of the sun,” said first author Thomas Jarboe, a UW professor of aeronautics and astronautics. “I really think we’re the first people that are telling you the nature and source of solar magnetic phenomena—how the sun works.”

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Quiet sun [image credit: NASA]

NASA finally agrees with our model estimate for cycle 25 published in 2013. It’ll be interesting to see how this pans out. Leif Svalgaard predicted that cycle 25 would be higher than 24, but lower than cycle 20.

Research now underway may have found a reliable new method to predict this solar activity. The Sun’s activity rises and falls in an 11-year cycle. The forecast for the next solar cycle says it will be the weakest of the last 200 years. The maximum of this next cycle – measured in terms of sunspot number, a standard measure of solar activity level – could be 30 to 50% lower than the most recent one. The results show that the next cycle will start in 2020 and reach its maximum in 2025.

The new research was led by Irina Kitiashvili, a researcher with the Bay Area Environmental Research Institute at NASA’s Ames Research Center, in California’s Silicon Valley. It combined observations from two NASA space missions – the Solar and Heliospheric Observatory and the Solar Dynamics Observatory – with data collected since 1976 from the ground-based National Solar Observatory.

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A Sunspot from the Next Solar Cycle

Posted: July 11, 2019 by oldbrew in Astronomy, Solar physics
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The transition from solar cycle 24 to 25 is…out there somewhere. But it seems AR2744 is likely to become known as ‘the first official sunspot of Solar Cycle 25.’

Spaceweather.com

July 8, 2019: Solar Cycle 25 is coming to life. For the second time this month, a sunspot from the next solar cycle has emerged in the sun’s southern hemisphere. Numbered “AR2744”, it is inset in this magnetic map of the sun’s surface from NASA’s Solar Dynamics Observatory:

How do we know this sunspot belongs to Solar Cycle 25? Its magnetic polarity tells us so. Southern sunspots from old Solar Cycle 24 have a -/+ polarity. This sunspot is the opposite: +/-. According to Hale’s Law, sunspots switch polarities from one solar cycle to the next. AR2744 is therefore a member of Solar Cycle 25.

Solar cycles always mix together at their boundaries. Right now we are experiencing the tail end of decaying Solar Cycle 24. AR2744 shows that we are simultaneously experiencing the first stirrings of Solar Cycle 25. The transition between Solar Cycle 24 and Solar Cycle…

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An important new solar paper by Prof Valentina Zharkova and co-authors S. J. Shepherd, S. I. Zharkov & E. Popova  published in ‘Nature’ has incorporated the solar-planetary theory we’ve been researching and advancing here at the talkshop over the last decade. As well as further developing her previous double dynamo theory which now accounts for the last several millennium’s solar grand minima and maxima, she includes discussion of Fairbridge, Mackey, Shirley, Charvatova and Abreu et al’s work. Central to the new hypothesis is the motion of the Sun around the barycentre of the solar system, described as the Solar Inertial Motion [SIM].

Left plot: the example of SIM trajectories of the Sun about the barycenter calculated from 1950 until 210034. Right plot: the cone of expanding SIM orbits of the Sun35 with the top showing 2D orbit projections similar to the left plot. Here there are three complete SIM orbits of the Sun, each of which takes about 179 years. Each solar orbit consists of about eight, 22-year solar cycles35. The total time span is, therefore, three 179-year solar cycles31, or about 600 years. Source: Adapted from Mackey35. Reproduced with permission from the Coastal Education and Research Foundation, Inc

Following my discussion with her at dinner following her talk in London last year, Zharkova now agrees with us that the SIM induced by planetary motion affects sunspot production and solar activity levels.

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‘The coronal heating problem in solar physics relates to the question of why the temperature of the Sun’s corona is millions of kelvins higher than that of the surface. Several theories have been proposed to explain this phenomenon but it is still challenging to determine which of these is correct’ — Wikipedia.

It’s one of the greatest and longest-running mysteries surrounding, quite literally, our sun—why is its outer atmosphere hotter than its fiery surface?

University of Michigan researchers believe they have the answer, and hope to prove it with help from NASA’s Parker Solar Probe, says Phys.org.

In roughly two years, the probe will be the first manmade craft to enter the zone surrounding the sun where heating looks fundamentally different than what has previously been seen in space.

This will allow them to test their theory that the heating is due to small magnetic waves travelling back and forth within the zone.

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Main solar system planets [image credit: Wikipedia]


No s**t Sherlock! Numerous independent researchers, some featured at the Talkshop, have been working along such lines for years with little apparent recognition and even a certain amount of negative reaction (like this), let’s say.

H/T Miles Mathis

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HZDR press release of May 27, 2019: New study corroborates the influence of planetary tidal forces on solar activity.

One of the big questions in solar physics is why the Sun’s activity follows a regular cycle of 11 years. Researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), an independent German research institute, now present new findings, indicating that the tidal forces of Venus, Earth and Jupiter influence the solar magnetic field, thus governing the solar cycle.

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