Posts Tagged ‘Sun’
Carrington Probabilities
March 16th, 2016 | 
Author: 
K7RA's 'Solar Update' in this week's ARRL News, mentions Jeff Foust's recent article in 'The Space Review', reminding us again of the dangers posed by a modern-day 'Carrington Event', also known as the 'Solar Storm of 1859'. A large solar flare in late August, hurled a monster-sized CME towards earth, making the 93 million mile journey in just 17.6 hours compared with the more normal rate of several days.
Huge auroras soon lit up the sky as far as central Mexico, Hawaii and the Caribbean. The aurora was so bright, it was reported that Rocky Mountain goldminers awoke in the middle of the night, and thinking morning had arrived, started to prepare breakfast. Telegraph lines and equipment burst into flame while some circuits continued to be usable with power supplies completely disconnected. The 1859 event still remains the most geoeffective solar storm since records have been kept.
Such an event today, of course, would wreak much more havoc ... probably having devastating consequences for decades and causing trillions of dollars of damage.
From Foust's article:
Was that, though, just a fluke event? .... Pete Riley, senior research scientist at Predictive Science Inc., offered a probabilistic forecast for the likelihood of another Carrington-like event, based on that storm’s estimated strength and measurements of the actual strength of solar storms over the last few decades. “If you the (sic) time between events, you can calculate the probability of the next event occurring within some unit of time,” he explained.
His estimate of the probability of another Carrington event is surprisingly high: about a 10 percent chance of such an event occurring over the next decade. “Ten percent is very, very high,” said William Murtaugh, assistant director for space weather at the White House’s Office of Science and Technology Policy (OSTP) ... “A one-percent probability over the course of the next one hundred years of a storm with an impact of that magnitude is considered very, very high and will motivate action.”
Interestingly, for this prediction, the actual strength of the solar storm of 1859 can only be estimated. If it was actually twice as strong as thought, then the probabilities drop from a (decade) 10% probability to just a 1% chance.
The U.S. government has recently set up a NASA multi-million budget funding proposal to study the likely effects of future large scale impacts and possible “response and resiliency capabilities” but it's not known if these will carry over to any new administration.
“Fortunately in space weather there’s no real politics,” Murtaugh said. “Both sides of House, both sides of the Senate, Republicans and Democrats, are both keen to work together to do something about this issue.”
The article has brought some interesting 'food for thought' comments, among them:
It's a little funny about how much energy is being spent advocating human spaceflight for colonization and settlement as a means to save the species, but so little is being devoted to specific threats to the species, and to individuals in particular. I could get killed in an asteroidal impact or a severe geomagnetic storm, but sending a shipload of people to Mars sure isn't going to protect me.
I am a member of Infragard, which is dedicated to supporting efforts to protect us from risks to our electrical grid and other critical infrastructure. A novel "One Second After" by William R. Forstchen accurately illustrates the effects of a similar intentional attack on our grid and how it creates a cascading collapse of our society. Gas stations cannot pump gas, food rots in the stores, more food cannot be delivered to all the needed locations, and the people who know how to fix things cannot reach where they are needed and also starve to death. The result of a severe Carrington event with no effective preparation or protection for the giant transformers could thus cause most of our population to starve in a few months. This risk is about 1% to 0.5 % per year and is like having everyone playing Russian roulette once a year with 200 pistols where just one is loaded.
A modern day 'Carrington repeat' does indeed give pause for thought but perhaps the generally predicted upcoming 'grand solar minimum' will buy scientists some extra time to come up with solutions for what will eventually occur ... and, one more thing's for certain ... it'll be a heck of an aurora!
Aurora On The Move
A recent posting to the Pacific Northwest VHF Society's reflector brought my attention to an interesting article describing the southward migration of the auroral zone.
According to the research paper published in the Proceedings of the National Academy of Sciences, the earth's magnetic field is gradually growing weaker, thus affecting its interaction with the solar wind.
The paper indicates that our present, abnormally high magnetic field, forces this interaction (auroras) to higher latitudes and as the field strength gradually weakens to more long-term average levels, auroras will be seen further south than we have been used to. The field has already weakened by about 10% over the past two hundred years and will continue to do so. Apparently it's all related to the regular 'flipping' of our magnetic field, with the most 'recent' flip taking place about 780,000 years ago.
So what does this mean for radio amateurs? Probably not a lot, in the immediate future but the unwanted effects to disturbances in the geomagnetic field will eventually be felt further and further to the south. Radio propagation in southern British Columbia has always been particularly sensitive to even very small disturbances in the field, particularly on the LF and MF bands. I am constantly amazed at how regions only 150 miles to the south or southeast of me are so much less affected than here, in the southern fringes of the auroral zone. VE7's don't claim to be in radio's 'black hole' without good reason.
LF Improving
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| courtesy: http://sdo.gsfc.nasa.gov/ |
After more than a week of horrendous geomagnetic activity, due mainly to coronal-hole streaming, it looks as if things are starting to settle down once again. One would never know it from looking at the sun's image as the source of the streaming is largely invisible in the visible light spectrum. Viewing at a different wavelength however, reveals the source of the disruption, now about to rotate out of view for a few weeks.
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| courtesy: http://sdo.gsfc.nasa.gov/ |
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| courtesy: http://wdc.kugi.kyoto-u.ac.jp/dst_realtime/presentmonth/index.html |
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| courtesy: http://www.noaa.gov/ |
Quiet Sun Not Enough
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| courtesy: http://sdo.gsfc.nasa.gov/ |
... the sun has been deathly quiet, as can be seen in yesterday's solar disk image.
It seems that just the 'normal' solar wind can disrupt things all on its own, without any solar flares or coronal mass ejections. In the late 70's, 'cracks' in the earth's magnetosphere were first observed... cracks that allowed even a quiet solar wind to actively interact with the earth's (normally protected) upper atmosphere. Apparently this is the present condition that has been disrupting normal propagation for the past many days.
The spaceweather.com web site has a nice explanation of how these cracks allow the Sun's Interplanetary Magnetic Field (IMF) to interact with the earth's field:
"Earth has a magnetic field, too. It forms a bubble around our planet called the magnetosphere, which deflects solar wind gusts. (Mars, which does not have a protective magnetosphere, has lost much of its atmosphere as a result of solar wind erosion.) Earth's magnetic field and the IMF come into contact at the magnetopause: a place where the magnetosphere meets the solar wind. Earth's magnetic field points north at the magnetopause. If the IMF points south -- a condition scientists call "southward Bz" -- then the IMF can partially cancel Earth's magnetic field at the point of contact.
When Bz is south, that is, opposite Earth's magnetic field, the two fields link up," explains Christopher Russell, a Professor of Geophysics and Space Physics at UCLA. "You can then follow a field line from Earth directly into the solar wind" -- or from the solar wind to Earth. South-pointing Bz's open a door through which energy from the solar wind can reach Earth's atmosphere!"
Earth's Bz has been pointing south during this entire period of poor propagation. Heavy ionization of the daylight D-layer, normally an 'absorber' of LF signals, has allowed reception of several NDB signals normally only heard at night. In fact, one of my favorite NDB propagation indicators, 25-watt YLJ in Meadow Lake, Saskatchewan, has been heard all day long on 406KHz for the past week as its signal skirts along the underside of the dense D-layer. These auroral conditions however, often enhance the path to the south Pacific and several western BCB DXers have reported excellent propagation to Australia and New Zealand in the pre-dawn hours.
Another indicator of LF propagation disturbance is the DST or Disturbance Storm Time index. This number gives an indication of the severity of the weakness in the magnetosphere, with numbers going further and further negative as the charged particles trapped in the magnetosphere increase in numbers.
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| courtesy:http://wdc.kugi.kyoto-u.ac.jp/dst_realtime/presentmonth/index.html |
The DST has been having a rough ride since the beginning of the month and as these numbers grow more positive and remain there, propagation will return to normal. With late September and October often being among the best months of the year for LF propagation, and with the sun now doing its part by remaining quiet, let's hope that the earth's magnetosphere will also co-operate and seal-up those propagation-killing cracks.
Our Amazing Sun and HF Radio Signal Propagation
Space Weather. The Sun-Earth Connection. Ionospheric radio propagation. Solar storms. Coronal Mass Ejections (CMEs). Solar flares and radio blackouts. All of these topics are interrelated for the amateur radio operator, especially when the activity involves the shortwave, or high-frequency, radiowave spectrum.
Learning about space weather and radio signal propagation via the ionosphere aids you in gaining a competitive edge in radio DX contests. Want to forecast the radio propagation for the next weekend so you know whether or not you should attend to the Honey-do list, or declare a radio day?
In the last ten years, amazing technological advances have been made in heliophysics research and solar observation. These advances have catapulted the amateur radio hobbyist into a new era in which computer power and easy access to huge amounts of data assist in learning about, observing, and forecasting space weather and to gain an understanding of how space weather impacts shortwave radio propagation, aurora propagation, and so on.
I hope to start “blogging” here about space weather and the propagation of radio waves, as time allows. I hope this finds a place in your journey of exploring the Sun-Earth connection and the science of radio communication.
With that in mind, I’d like to share some pretty cool science. Even though the video material in this article are from 2010, they provide a view of our Sun with the stunning solar tsunami event:
On August 1, 2010, the entire Earth-facing side of the sun erupted in a tumult of activity. There was a C3-class solar flare, a solar tsunami, multiple plasma-filled filaments of magnetism lifting off the stellar surface, large-scale shaking of the solar corona, radio bursts, a coronal mass ejection and more!
At approximately 0855 UTC on August 1, 2010, a C3.2 magnitude soft X-ray flare erupted from NOAA Active Sunspot Region 11092 (we typically shorten this by dropping the first digit: NOAA AR 1092).
At nearly the same time, a massive filament eruption occurred. Prior to the filament’s eruption, NASA’s Solar Dynamics Observatory (SDO) AIA instruments revealed an enormous plasma filament stretching across the sun’s northern hemisphere. When the solar shock wave triggered by the C3.2-class X-ray explosion plowed through this filament, it caused the filament to erupt, sending out a huge plasma cloud.
In this movie, taken by SDO AIA at several different Extreme Ultra Violet (EUV) wavelengths such as the 304- and 171-Angstrom wavelengths, a cooler shock wave can be seen emerging from the origin of the X-ray flare and sweeping across the Sun’s northern hemisphere into the filament field. The impact of this shock wave may propelled the filament into space.
This movie seems to support this analysis: Despite the approximately 400,000 kilometer distance between the flare and the filament eruption, they appear to erupt together. How can this be? Most likely they’re connected by long-range magnetic fields (remember: we cannot see these magnetic field lines unless there is plasma riding these fields).
In the following video clip, taken by SDO AIA at the 304-Angstrom wavelength, a cooler shock wave can be seen emerging from the origin of the X-ray flare and sweeping across the sun’s northern hemisphere into the filament field. The impact of this shock wave propelled the filament into space. This is in black and white because we’re capturing the EUV at the 304-Angstrom wavelength, which we cannot see. SDO does add artificial color to these images, but the raw footage is in this non-colorized view.
The followling video shows this event in the 171-Angstrom wavelength, and highlights more of the flare event:
The following related video shows the “resulting” shock wave several days later. Note that this did NOT result in anything more than a bit of aurora seen by folks living in high-latitude areas (like Norway, for instance).
This fourth video sequence (of the five in the first video shown in this article) shows a simulation model of real-time passage of the solar wind. In this segment, the plasma cloud that was ejected from this solar tsunami event is seen in the data and simulation, passing by Earth and impacting the magnetosphere. This results in the disturbance of the geomagnetic field, triggering aurora and ionospheric depressions that degrade shortwave radio wave propagation.
At about 2/3rd of the way through, UTC time stamp 1651 UTC, the shock wave hits the magnetosphere.
This is a simulation derived from satellite data of the interaction between the solar wind, the earth’s magnetosphere, and earth’s ionosphere. This triggered aurora on August 4, 2010, as the geomagnetic field became stormy (Kp was at or above 5).
While this is an amazing event, a complex series of eruptions involving most of the visible surface of the sun occurred, ejecting plasma toward the Earth, the energy that was transferred by the plasma mass that was ejected by the two eruptions (first, the slower-moving coronal mass ejection originating in the C-class X-ray flare at sunspot region 1092, and, second, the faster-moving plasma ejection originating in the filament eruption) was “moderate.” This event, especially in relationship with the Earth through the Sun-Earth connection, was rather low in energy. It did not result in any news-worthy events on Earth–no laptops were fried, no power grids failed, and the geomagnetic activity level was only moderate, with limited degradation observed on the shortwave radio spectrum.
This “Solar Tsunami” is actually categorized as a “Moreton wave”, the chromospheric signature of a large-scale solar coronal shock wave. As can be seen in this video, they are generated by solar flares. They are named for American astronomer, Gail Moreton, an observer at the Lockheed Solar Observatory in Burbank who spotted them in 1959. He discovered them in time-lapse photography of the chromosphere in the light of the Balmer alpha transition.
Moreton waves propagate at a speed of 250 to 1500 km/s (kilometers per second). A solar scientist, Yutaka Uchida, has interpreted Moreton waves as MHD fast-mode shock waves propagating in the corona. He links them to type II radio bursts, which are radio-wave discharges created when coronal mass ejections accelerate shocks.
I will be posting more of these kinds of posts, some of them explaining the interaction between space weather and the propagation of radio signals.
For live space weather and radio propagation, visit http://SunSpotWatch.com/. Be sure to subscribe to my YouTube channel: https://YouTube.com/NW7US.
The fourth video segment is used by written permission, granted to NW7US by NICT. The movie is copyright@NICT, Japan. The rest of the video is courtesy of SDO/AIA and NASA. Music is courtesy of YouTube, from their free-to-use music library. Video copyright, 2015, by Tomas Hood / NW7US. All rights reserved.
Stunning Video of the Sun Over Five Years, by SDO
Watch this video on a large screen. (It is HD). Discuss. Share.
This video features stunning clips of the Sun, captured by SDO from each of the five years since SDO’s deployment in 2010. In this movie, watch giant clouds of solar material hurled out into space, the dance of giant loops hovering in the corona, and huge sunspots growing and shrinking on the Sun’s surface.
April 21, 2015 marks the five-year anniversary of the Solar Dynamics Observatory (SDO) First Light press conference, where NASA revealed the first images taken by the spacecraft. Since then, SDO has captured amazingly stunning super-high-definition images in multiple wavelengths, revealing new science, and captivating views.
February 11, 2015 marks five years in space for NASA’s Solar Dynamics Observatory, which provides incredibly detailed images of the whole Sun 24 hours a day. February 11, 2010, was the day on which NASA launched an unprecedented solar observatory into space. The Solar Dynamics Observatory (SDO) flew up on an Atlas V rocket, carrying instruments that scientists hoped would revolutionize observations of the Sun.
Capturing an image more than once per second, SDO has provided an unprecedentedly clear picture of how massive explosions on the Sun grow and erupt. The imagery is also captivating, allowing one to watch the constant ballet of solar material through the sun’s atmosphere, the corona.
The imagery in this “highlight reel” provide us with examples of the kind of data that SDO provides to scientists. By watching the sun in different wavelengths (and therefore different temperatures, each “seen” at a particular wavelength that is invisible to the unaided eye) scientists can watch how material courses through the corona. SDO captures images of the Sun in 10 different wavelengths, each of which helps highlight a different temperature of solar material. Different temperatures can, in turn, show specific structures on the Sun such as solar flares or coronal loops, and help reveal what causes eruptions on the Sun, what heats the Sun’s atmosphere up to 1,000 times hotter than its surface, and why the Sun’s magnetic fields are constantly on the move.
Coronal loops are streams of solar material traveling up and down looping magnetic field lines). Solar flares are bursts of light, energy and X-rays. They can occur by themselves or can be accompanied by what’s called a coronal mass ejection, or CME, in which a giant cloud of solar material erupts off the Sun, achieves escape velocity and heads off into space.
This movie shows examples of x-ray flares, coronal mass ejections, prominence eruptions when masses of solar material leap off the Sun, much like CMEs. The movie also shows sunspot groups on the solar surface. One of these sunspot groups, a magnetically strong and complex region appearing in mid-January 2014, was one of the largest in nine years as well as a torrent of intense solar flares. In this case, the Sun produced only flares and no CMEs, which, while not unheard of, is somewhat unusual for flares of that size. Scientists are looking at that data now to see if they can determine what circumstances might have led to flares eruptions alone.
Scientists study these images to better understand the complex electromagnetic system causing the constant movement on the sun, which can ultimately have an effect closer to Earth, too: Flares and another type of solar explosion called coronal mass ejections can sometimes disrupt technology in space as well as on Earth (disrupting shortwave communication, stressing power grids, and more). Additionally, studying our closest star is one way of learning about other stars in the galaxy.
Goddard built, operates and manages the SDO spacecraft for NASA’s Science Mission Directorate in Washington, D.C. SDO is the first mission of NASA’s Living with a Star Program. The program’s goal is to develop the scientific understanding necessary to address those aspects of the sun-Earth system that directly affect our lives and society.
A Solar flare, A CME, A Proton Storm: Magnitude M2.5 X-ray Flare
Watch this amazing explosion on the Sun. From sunspot complex 1226-1227 comes an X-ray Flare peaking at a magnitude of M2.5 at 0640 UTC on 7 June, 2011.
Source: https://www.youtube.com/watch?v=KQMrRu8BWDo
This X-ray flare hurled a massive coronal mass ejection (CME) toward the Earth. This not-squarely Earth-directed CME is moving at 1400 km/s according to NASA models. The CME did not deliver even a noticeable glancing blow to Earth’s magnetic field late June 8th or June 9th.
What can be seen clearly in this movie is one of the most spectacular prominence eruptions ever observed. In fact, one could call it a “prominence explosion”. The prominence material expanded to a volume some 75 times as big across as the earth!
This X-ray flare also triggered an S1-level solar radiation storm, causing a long-lasting polar cap absorption (PCA) event. A polar cap absorption (PCA) event affects the propagation of a shortwave radio signal as it makes its way over the polar regions. In short, radio communications on lower shortwave radio frequencies become more difficult, as those radio signals are absorbed by the ionosphere (in the D-region) over the polar regions.
What does this mean in real-world communications? Trans-polar airline pilots may find it more difficult to communicate with regional air traffic control, shortwave radio listeners who want to hear a broadcast from a country by receiving a transmission from a country by way of a transmission beamed over the pole (like, from Europe into the USA via the North Pole), or other such communications, will find those signals all but gone. The stronger the PCA event, the higher the frequencies absorbed over the polar regions, with the greatest absorption occurring at the lower frequencies.
This movie spans the period of time from 0300 UTC through 1556 UTC, and is composed of the 171-Angstrom, 304-Angstrom, and 335-Angstrom wavelength views as captured by the filters of the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA). In this movie, the AIA instruments capture the Sun’s extreme ultraviolet light and reveal a very large eruption of cool gas. It is somewhat unique because at many places in the eruption there seems to be even cooler material–at temperatures less than 80,000 K.
The following is a linked video that is part of this event: http://www.youtube.com/watch?v=L4CsjcUGoaw
Watch as we zoom out to see a total view of the June 7, 2011 moderately-powerful X-ray Flare and Prominence Eruption. This movie will give you a full perspective of the immense size of this prominence eruption as it spews out away from the Sun.
The X-ray Flare peaked at a moderate magnitude of M2.5 at 0640 UTC, but unleashed a huge prominence eruption. The massive cloud of plasma was ejected out into interplanetary space, but missed the Earth. This movie stars with a “close-up” view by the Solar Dynamics Observatory at a combined wavelength view at 94 and 304 Angstroms. Then, the movie views the event further back through the eyes of the COR1 spacecraft (with the SDO AIA 304 image superimposed in the middle). Next, we zoom out to the COR2 spacecraft and superimpose the COR1 and SDO views. Then, we zoom further back to the H1 view… and finally look again at the event close-up.
More info: http://sunspotwatch.com/
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Source: SDO AIA NASA SOHO
