Solar Astronomy Archives

June 21, 2008December 24, 2015 by Ian O'Neill

2012: No Killer Solar Flare

Could a solar flare destroy the Earth in 2012?

We could be in for a huge firework display in 2012. The Sun will be approaching the peak of its 11-year cycle, called “solar maximum”, so we can expect a lot of solar activity. Some predictions put the solar maximum of Solar Cycle 24 even more energetic than the last solar maximum in 2002-2003 (remember all those record breaking X-class flares?). Solar physicists are already getting excited about this next cycle and new prediction methods are being put to good use. But should we be worried?

Related 2012 articles:

According to one of the many Doomsday scenarios we have been presented with in the run-up to the Mayan Prophecy-fuelled “end of the world” in the year 2012, this scenario is actually based on some science. What’s more, there may be some correlation between the 11-year solar cycle and the time cycles seen in the Mayan calendar, perhaps this ancient civilization understood how the Sun’s magnetism undergoes polarity changes every decade or so? Plus, religious texts (such as the Bible) say that we are due for a day of judgement, involving a lot of fire and brimstone. So it looks like we are going to get roasted alive by our closest star on December 21st, 2012!

Before we go jumping to conclusions, take a step back and think this through. Like most of the various ways the world is going to end in 2012, the possibility of the Sun blasting out a huge, Earth-damaging solar flare is very attractive to the doomsayers out there. But let’s have a look at what really happens during an Earth-directed solar flare event, the Earth is actually very well protected. Although some satellites may not be…

The Earth has evolved in a highly radioactive environment. The Sun constantly fires high-energy particles from its magnetically dominated surface as the solar wind. During solar maximum (when the Sun is at its most active), the Earth may be unlucky enough to be staring down the barrel of an explosion with the energy of 100 billion Hiroshima-sized atomic bombs. This explosion is known as a solar flare and the effects of which can cause problems here on Earth.

Before we look at the Earth-side effects, let’s have a look at the Sun and briefly understand why it gets so angry every 11 years or so.

The Solar Cycle

First and foremost, the Sun has a natural cycle with a period of approximately 11 years. During the lifetime of each cycle, the magnetic field lines of the Sun are dragged around the solar body by differential rotation at the solar equator. This means that the equator is spinning faster than the magnetic poles. As this continues, solar plasma drags the magnetic field lines around the Sun, causing stress and a build up of energy (an illustration of this is pictured). As magnetic energy increases, kinks in the magnetic flux form, forcing them to the surface. These kinks are known as coronal loops which become more numerous during periods of high solar activity.

This is where the sunspots come in. As coronal loops continue to pop up over the surface, sunspots appear too, often located at the loop footpoints. Coronal loops have the effect of pushing the hotter surface layers of the Sun (the photosphere and chromosphere) aside, exposing the cooler convection zone (the reasons why the solar surface and atmosphere is hotter than the solar interior is down to the coronal heating phenomenon). As magnetic energy builds up, we can expect more and more magnetic flux to be forced together. This is when a phenomenon known as magnetic reconnection occurs.

Reconnection is the trigger for solar flares of various sizes. As previously reported, solar flares from “nanoflares” to “X-class flares” are very energetic events. Granted, the largest flares my generate enough energy for 100 billion atomic explosions, but don’t let this huge figure concern you. For a start, this flare occurs in the low corona, right near the solar surface. That’s nearly 100 million miles away (1AU). The Earth is nowhere close to the blast.

As the solar magnetic field lines release a huge amount of energy, solar plasma is accelerated and confined within the magnetic environment (solar plasma is superheated particles like protons, electrons and some light elements such as helium nuclei). As the plasma particles interact, X-rays may be generated if the conditions are right and bremsstrahlung is possible. (Bremsstrahlung occurs when charged particles interact, resulting in X-ray emission.) This may create an X-ray flare.

The Problem with X-ray Solar Flares

The biggest problem with an X-ray flare is that we get little warning when it is going to happen as X-rays travel at the speed of light (one of the record breaking 2003 solar flares is pictured left). X-rays from an X-class flare will reach the Earth in around eight minutes. As X-rays hit our atmosphere, they are absorbed in the outermost layer called the ionosphere. As you can guess from the name, this is a highly charged, reactive environment, full of ions (atomic nuclei, and free electrons).

During powerful solar events such as flares, rates of ionization between X-rays and atmospheric gases increase in the D and E region layers of the ionosphere. There is a sudden surge in electron production in these layers. These electrons can cause interference to the passage of radio waves through the atmosphere, absorbing short wave radio signals (in the high frequency range), possibly blocking global communications. These events are known as “Sudden Ionospheric Disturbances” (or SIDs) and they become commonplace during periods of high solar activity. Interestingly, the increase in electron density during a SID boosts the propagation of Very Low Frequency (VLF) radio, a phenomenon scientists use to measure the intensity of X-rays coming from the Sun.

Coronal Mass Ejections?

X-ray solar flare emissions are only part of the story. If the conditions are right, a coronal mass ejection (CME) might be produced at the site of the flare (although either phenomenon can occur independently). CMEs are slower than the propagation of X-rays, but their global effects here on Earth can be more problematic. They may not travel at the speed of light, but they still travel fast; they can travel at a rate of 2 million miles per hour (3.2 million km/hr), meaning they may reach us in a matter of hours.

This is where much effort is being put into space weather prediction. We have a handful of spacecraft sitting between the Earth and the Sun at the Earth-Sun Lagrangian (L₁) point with sensors on board to measure the energy and intensity of the solar wind. Should a CME pass through their location, energetic particles and the interplanetary magnetic field (IMF) can be measured directly. One mission called the Advanced Composition Explorer (ACE) sits in the L₁ point and provides scientists with up to an hour notice on the approach of a CME. ACE teams up with the Solar and Heliospheric Observatory (SOHO) and the Solar TErrestrial RElations Observatory (STEREO), so CMEs can be tracked from the lower corona into interplanetary space, through the L₁ point toward Earth. These solar missions are actively working together to provide space agencies with advanced notice of an Earth-directed CME.

So what if a CME reaches Earth? For a start, much depends on the magnetic configuration of the IMF (from the Sun) and the geomagnetic field of the Earth (the magnetosphere). Generally speaking, if both magnetic fields are aligned with polarities pointing in the same direction, it is highly probable that the CME will be repelled by the magnetosphere. In this case, the CME will slide past the Earth, causing some pressure and distortion on the magnetosphere, but otherwise passing without a problem. However, if the magnetic field lines are in an anti-parallel configuration (i.e. magnetic polarities in opposite directions), magnetic reconnection may occur at the leading edge of the magnetosphere.

In this event, the IMF and magnetosphere will merge, connecting the Earth’s magnetic field with the Sun’s. This sets the scene for one of the most awe inspiring events in nature: the aurora.

Satellites in Peril
As the CME magnetic field connects with the Earth’s, high energy particles are injected into the magnetosphere. Due to solar wind pressure, the Sun’s magnetic field lines will fold around the Earth, sweeping behind our planet. The particles injected in the “dayside” will be funnelled into the polar regions of the Earth where they interact with our atmosphere, generating light as aurorae. During this time, the Van Allen belt will also become “super-charged”, creating a region around the Earth that could cause problems to unprotected astronauts and any unshielded satellites. For more on the damage that can be caused to astronauts and spacecraft, check out “Radiation Sickness, Cellular Damage and Increased Cancer Risk for Long-term Missions to Mars” and “New Transistor Could Side-Step Space Radiation Problem.”

As if the radiation from the Van Allen belt wasn’t enough, satellites could succumb to the threat of an expanding atmosphere. As you’d expect, as if the Sun hits the Earth with X-rays and CMEs, there will be inevitable heating and global expansion of the atmosphere, possibly encroaching into satellite orbital altitudes. If left unchecked, an aerobraking effect on satellites could cause them to slow and drop in altitude. Aerobraking has been used extensively as a space flight tool to slow spacecraft down when being inserted into orbit around another planet, but this will have an adverse effect on satellites orbiting Earth as any slowing of velocity could cause it to re-enter the atmosphere.

We Feel the Effects on the Ground Too

Although satellites are on the front line, if there is a powerful surge in energetic particles entering the atmosphere, we may feel the adverse effects down here on Earth too. Due to the X-ray generation of electrons in the ionosphere, some forms of communication may become patchy (or be removed all together), but this isn’t all that can happen. Particularly in high-latitude regions, a vast electric current, known as an “electrojet”, may form through the ionosphere by these incoming particles. With an electric current comes a magnetic field. Depending on the intensity of the solar storm, currents may be induced down here on the ground, possibly overloading national power grids. On March 13th 1989, six million people lost power in the Quebec region of Canada after a huge increase in solar activity caused a surge from ground-induced currents. Quebec was paralysed for nine hours whilst engineers worked on a solution to the problem.

Can Our Sun Produce a Killer Flare?

The short answer to this is “no”.

The longer answer is a little more involved. Whilst a solar flare from out Sun, aimed directly at us, could cause secondary problems such as satellite damage and injury to unprotected astronauts and blackouts, the flare itself is not powerful enough to destroy Earth, certainly not in 2012. I dare say, in the far future when the Sun begins to run out of fuel and swell into a red giant, it might be a bad era for life on Earth, but we have a few billion years to wait for that to happen. There could even be the possibility of several X-class flares being launched and by pure bad luck we may get hit by a series of CMEs and X-ray bursts, but none will be powerful to overcome our magnetosphere, ionosphere and thick atmosphere below.

“Killer” solar flares have been observed on other stars. In 2006, NASA’s Swift observatory saw the largest stellar flare ever observed 135 light-years away. Estimated to have unleashed an energy of 50 million trillion atomic bombs, the II Pegasi flare will have wiped out most life on Earth if our Sun fired X-rays from a flare of that energy at us. However, our Sun is not II Pegasi. II Pegasi is a violent red giant star with a binary partner in a very close orbit. It is believed the gravitational interaction with its binary partner and the fact II Pegasi is a red giant is the root cause behind this energetic flare event.

Doomsayers point to the Sun as a possible Earth-killer source, but the fact remains that our Sun is a very stable star. It does not have a binary partner (like II Pegasi), it has a predictable cycle (of approximately 11 years) and there is no evidence that our Sun contributed to any mass extinction event in the past via a huge Earth-directed flare. Very large solar flares have been observed (such as the 1859 Carrington white light flare)… but we are still here.

In an added twist, solar physicists are surprised by the lack of solar activity at the start of this 24th solar cycle, leading to some scientists to speculate we might be on the verge of another Maunder minimum and “Little Ice Age”. This is in stark contrast to NASA solar physicist’s 2006 prediction that this cycle will be a “doozy”.

This leads me to conclude that we still have a long way to go when predicting solar flare events. Although space weather prediction is improving, it will be a few years yet until we can read the Sun accurately enough to say with any certainty just how active a solar cycle is going to be. So, regardless of prophecy, prediction or myth, there is no physical way to say that the Earth will be hit by any flare, let alone a big one in 2012. Even if a big flare did hit us, it will not be an extinction event. Yes, satellites may be damaged, causing secondary problems such as a GPS loss (which might disrupt air traffic control for example) or national power grids may be overwhelmed by auroral electrojets, but nothing more extreme than that.

But hold on, to sidestep this issue, doomsayers now tell us that a large solar flare will hit us just as the Earth’s geomagnetic field weakens and reverses, leaving us unprotected from the ravages of a CME… The reasons why this is not going to happen in 2012 is worthy of its own article. So, look out for the next 2012 article “2012: No Geomagnetic Reversal“.

Leading image credits: MIT (supernova simulation), NASA/JPL (solar active region in EUV). Effects and editing: myself.

June 12, 2008December 24, 2015 by Ian O'Neill

Where are the Sunspots? Are we in for a Quiet Solar Cycle?

The Suns photosphere is looking particulary boring (NASA/SOHO)

So what’s up with our Sun? Is it going through a depression? It seems as if our closest star is experiencing a surprisingly uneventful couple of years. Solar minimum has supposedly passed and we should be seeing a lot more magnetic activity, and we certainly should be observing lots more sunspots. Space weather forecasts have been putting Solar Cycle 24 as a historically active cycle… but so far, nothing. So what’s the problem? Is it a ticking bomb, waiting to shock us with a huge jump in solar activity, flares and CMEs over a few months? Or could this lack of activity a prelude to a very boring few years, possibly leading the Earth toward another Ice Age?

It’s funny. Just as we begin to get worried that the next solar maximum is going to unleash all sorts of havoc on Earth (i.e. NASA’s 2006 solar storm warning), scientists begin to get concerned as to whether there is going to be a solar maximum at all. In a conference last week at Montana State University, solar physicists discussed the possibility that the Sun could be facing a long period of calm, leading to the concern that there could be another Maunder Minimum. The Maunder Minimum (named after the late 19th Century solar astronomer Edward W. Maunder, who discovered the phenomenon) was a 17th Century, 30-year period when very few sunspots were observed on the disk of the Sun. It is thought by many scientists that this period contributed to what became known as the “Little Ice Age” here on Earth. As the Sun provides Earth with all its energy, during extended periods when the solar output is lower than average, it seems possible a lack of sunspots on the Sun (i.e. low activity) may be linked with periods of cold down here.

“It continues to be dead. That’s a small concern, a very small concern.” – Saku Tsuneta, National Astronomical Observatory of Japan and program manager for the Hinode solar mission.

However, solar physicists are not too worried about this possibility, after all, it’s only been two years since solar minimum. Although activity has been low for the beginning of Cycle 24, sunspots have not been non-existent. In January of this year, a newborn spot was observed, as expected, in high latitude regions. More spots were seen in April. In March, sunspots from the previous solar cycle even made an appearance, putting on an unexpected show of flares and coronal mass ejections (CMEs).

As pointed out by David Hathaway, a solar physicist at NASA’s Marshall Space Flight Center, the fact that sunspots have already been observed in this new cycle means that it is highly unlikely we face anything as extreme as another Maunder Minimum. Hathaway says there is nothing unusual about having a relatively understated solar cycle after several particularly active cycles. Solar Cycle 23 was a very active period for the Sun with a greater than average number of sunspots observed on the solar surface.

It appears there are two different predictions for the activity level of the next solar cycle. On the one hand we have scientists that think this cycle might be below average, and on the other hand we have scientists who believe the next cycle will be the biggest yet. We certainly have a long way to go before we can begin making any accurate solar forecasts…

Source: Space.com

May 31, 2008December 24, 2015 by Ian O'Neill

Warm Coronal Loops May Hold the Key to Hot Solar Atmosphere

Coronal loops as imaged by TRACE at 171 Angstroms (1 million deg C) (NASA/TRACE)

Coronal loops, the elegant and bright structures threading through the solar surface and into the solar atmosphere, are key to understanding why the corona is so hot. Yes, it’s the Sun, and yes, it’s hot, but its atmosphere is too hot. The puzzle as to why the solar corona is hotter than the Sun’s photosphere has kept solar physicists busy since the mid-twentieth century, but with the help of modern observatories and advanced theoretical models, we now have a pretty good idea what is causing this. So is the problem solved? Not quite…

So why are solar physicists so interested in the solar corona anyway? To answer this, I’ll pull up an excerpt from my first ever Universe Today article:

…measurements of coronal particles tell us the atmosphere of the Sun is actually hotter than the Suns surface. Traditional thinking would suggest that this is wrong; all sorts of physical laws would be violated. The air around a light bulb isn’t hotter than the bulb itself, the heat from an object will decrease the further away you measure the temperature (obvious really). If you’re cold, you donâ€™t move away from the fire, you get closer to it! – from “Hinode Discovers Sun’s Hidden Sparkle“, Universe Today, December 21st, 2007

This isn’t only an academic curiosity. Space weather originates from the lower solar corona; understanding the mechanisms behind coronal heating has wide-ranging implications for predicting energetic (and damaging) solar flares and forecasting interplanetary conditions.

So, the coronal heating problem is an interesting issue and solar physicists are hot on the trail of the answer to why the corona is so hot. Magnetic coronal loops are central to this phenomenon; they are at the base of the solar atmosphere and experience rapid heating with a temperature gradient from tens of thousands of Kelvin (in the chromosphere) to tens of millions of Kelvin (in the corona) over a very short distance. The temperature gradient acts across a thin transition region (TR), which varies in thickness, but can be only a few hundreds of kilometers thick in places.

These bright loops of hot solar plasma may be easy to see, but there are many discrepancies between the observation of the corona and coronal theory. The mechanism(s) responsible for heating the loops have proven to be hard to pin down, particularly when trying to understand the dynamics of “intermediate temperature” (a.k.a. “warm”) coronal loops with plasma heated to around one million Kelvin. We are getting closer to solving this puzzle which will aid space weather predictions from the Sun to the Earth, but we need to work out why the theory is not the same as what we are seeing.

Solar physicists have been divided on this topic for some time. Is coronal loop plasma heated by intermittent magnetic reconnection events throughout the length of a coronal loop? Or are they heated by some other steady heating very low in the corona? Or is it a bit of both?

I actually spent four years wrestling with this issue whilst working with the Solar Group at the University of Wales, Aberystwyth, but I was on the side of “steady heating”. There are several possibilities when considering the mechanisms behind steady coronal heating, my particular area of study was AlfvÃ©n wave production and wave-particle interactions (shameless self-promotion… my 2006 thesis: Quiescent Coronal Loops Heated By Turbulence, just in case you have a spare, dull weekend ahead of you).

James Klimchuk from the Goddard Space Flight Center’s Solar Physics Laboratory in Greenbelt, Md., takes a different opinion and favours the nanoflare, impulsive heating mechanism, but he is highly aware that other factors may come into play:

“It has become clear in recent years that coronal heating is a highly dynamic process, but inconsistencies between observations and theoretical models have been a major source of heartburn. We have now discovered two possible solutions to this dilemma: energy is released impulsively with the right mix of particle acceleration and direct heating, or energy is released gradually very close to the solar surface.” – James Klimchuk

Nanoflares are predicted to maintain warm coronal loops at their fairly steady 1 million Kelvin. We know the loops are this temperature as they emit radiation in the extreme ultraviolet (EUV) wavelengths, and a host of observatories have been built or sent into space with instruments sensitive to this wavelength. Space-based instruments such as the EUV Imaging Telescope (EIT; onboard the NASA/ESA Solar and Heliospheric Observatory), NASA’s Transition Region and Coronal Explorer (TRACE), and the recently operational Japanese Hinode mission have all had their successes, but many coronal loop breakthroughs occurred after the launch of TRACE back in 1998. Nanoflares are very hard to observe directly as they occur over spatial scales so small, they cannot be resolved by the current instrumentation. However, we are close, and there is a trail of coronal evidence pointing to these energetic events.

“Nanoflares can release their energy in different ways, including the acceleration of particles, and we now understand that the right mix of particle acceleration and direct heating is one way to explain the observations.” – Klimchuk.

Slowly but surely, theoretical models and observation are coming together, and it seems that after 60 years of trying, solar physicists are close to understanding the heating mechanisms behind the corona. By looking at how nanoflares and other heating mechanisms may influence each other, it is very likely that more than one coronal heating mechanism is at play…

Aside: Out of interest, nanoflares will occur at any altitude along the coronal loop. Although they may be called nanoflares, by Earth standards, they are huge explosions. Nanoflares release an energy of 10²⁴-10²⁶ erg (that is 10¹⁷-10¹⁹ Joules). This is the equivalent of approximately 1,600 to 160,000 Hiroshima-sized atomic bombs (with the explosive energy of 15 kilotonnes), so there is nothing nano about these coronal explosions! But on the comparison with the standard X-ray flares the Sun generates from time to time with a total energy of 6×10²⁵ Joules (over 100 billion atomic bombs), you can see how nanoflares get their name…

Original source: NASA

May 27, 2008December 24, 2015 by Nancy Atkinson

Solar Blast Seen in Unprecedented Detail (Video)

Periodically our sun blasts streams of hot, ionized gas into the solar system. These eruptions, called coronal mass ejections or CMEs pose a potential threat to astronauts or satellites if aimed at Earth. On April 9, the Sun erupted with a CME, and because the eruption was located on the edge or limb of the sun, it was observed in unprecedented detail by a fleet of spacecraft, revealing new features that are predicted by computer models but are otherwise difficult to see, even for specialized sun-watching spacecraft. From these observations, astronomers have been able to create an animation of this spectacular event.

When a CME occurs, usually spacecraft watching the event need to protect themselves from the bright X-ray solar flare associate with a CME. However, since the April 9 CME occurred on the edge or limb of the Sun as viewed from Earth, the solar flare was hidden from view, which allowed spacecraft to take longer exposures and uncover fainter structures than usual.

â€œObservations like this are very rare,â€ said Smithsonian astronomer Ed DeLuca.

Using the Smithsonian-developed X-ray Telescope (XRT) aboard the Japanese Hinode sun-watching satellite, astronomers saw a spiral (helical) magnetic structure unwind as it left the Sun during the CME. Such unwinding can release energy as the magnetic field goes from a more twisted to a less twisted configuration, thereby helping to power the eruption.

Hours later, XRT revealed an inflow of material toward a feature that appears as a bright lineâ€”actually an object known as a current sheet seen edge-on. A current sheet is a thin, electrified sheet of gas where oppositely directed magnetic field lines annihilate one another in a process known as magnetic reconnection. The extended observations from XRT show that magnetic fields flow in toward the current sheet for many hours after the eruption, progressing first toward the sheet and then down to the sunâ€™s surface.

The astronomers were able to create an animation of the event.

They also determined that the temperature of the current sheet is between 5 and 18 million degrees Fahrenheit, which matches previous measurements higher up in the corona by the Ultraviolet Coronagraph Spectrometer on the SOHO spacecraft.

Astronomers study these explosions in hope of being able to predict them and provide â€œspace weatherâ€ forecasts.

Original News Source: Harvard Smithsonian Center for Astrophysics

May 19, 2008December 24, 2015 by Nancy Atkinson

Wow! Satellite Catches Bright Solar Flare From a Another Star

Artist's depiction of red-dwarf-flare. Image credit: Casey Reed/NASA

NASA’s Swift satellite picked up one of the brightest solar flares ever seen — not from our own sun, but a star 16 light-years away. This flare packed the power of thousands of solar flares combined, and a flare of this magnitude from our own sun would have stripped Earth’s atmosphere and sterilized the planet. Astronomers say the flare would have been visible to the naked eye on April 25, 2008 if the star had been easily observable in the night sky at the time. As it was, the flare’s brightness caused Swifts’ Ultraviolet/Optical Telescope to shut down for safety reasons. But Swift was able to study the flare for over 8 hours with its X-ray capabilities.

The Swift satellite normally searches for gamma ray bursts, and is surrounded with detectors that look for bursts of light. The spacecraft then “swiftly” and autonomously re-points itself to the location of the burst. However, this was no gamma ray burst, just a solar flare. But what a solar flare!

The star, EV Lacertae, is a basic red dwarf, the most common type of star in the universe. It shines with only one percent of the Sun’s light, and contains only a third of the Sun’s mass. It’s one of our closest stellar neighbors, but normally is not visible with the naked eye, as it holds a magnitude of -10.

“Here’s a small, cool star that shot off a monster flare. This star has a record of producing flares, but this one takes the cake,” says Rachel Osten, from NASA’s Goddard Space Flight Center. “Flares like this would deplete the atmospheres of life-bearing planets, sterilizing their surfaces.”

Astronomers say EV Lacertae is like an unruly child that throws frequent temper tantrums. It’s a relatively young star at a few hundred million years of age. But it’s a fast rotating star which generates a strong magnetic field, about 100 times as magnetically powerful as the Sun’s field. The energy stored in its magnetic field powers these giant flares.

The flare’s incredible brightness enabled Swift to make detailed measurements in X-ray, as the star remained bright in x-rays for about 8 hours. “This gives us a golden opportunity to study a stellar flare on a second-by-second basis to see how it evolved,” says Stephen Drake of NASA Goddard.

Flares release energy across the electromagnetic spectrum, but the extremely high gas temperatures produced by flares can only be studied with high-energy telescopes like those on Swift. Swift’s wide field and rapid repointing capabilities, designed to study gamma-ray bursts, make it ideal for studying stellar flares. Most other X-ray observatories have studied this star and others like it, but they have to be extremely lucky to catch and study powerful flares due to their much smaller fields of view.

Original News Source: NASA

May 5, 2008December 24, 2015 by Nancy Atkinson

Mission to the Sun

Astronomy — Solar Probe Spacecraft. Credit: NASA/Johns Hopkins University Applied Physics Laboratory

A mission to the sun is difficult stuff. For 30 years scientists and engineers have struggled with developing a spacecraft that could survive the harsh environment close to the sun, but always ended up running into insurmountable technology limitations or blowing the top off the budget. But now the Applied Physics Lab believes they have come up with a plan that will work, and NASA has given them the go-ahead to get a mission ready by 2015. And contrary to the old joke about a mission to the sun, the new Solar Probe won’t have an easy time of it by just heading to the sun at night!

The Solar Probe mission will come within 6.6 million kilometers (4.1 million miles) of the sun to study the streams of charged particles the sun hurls into space. The spacecraft will actually be within the sun’s corona — its outer atmosphere — where the solar wind is produced. At closest approach the Solar Probe will zip past the sun at 210 km (125 miles) per second, protected by a carbon-composite heat shield able to withstand up to 1425 degrees Celsius (2,600 degrees Fahrenheit) and survive blasts of radiation and energized dust at levels not experienced by any previous spacecraft.

The spacecraft will weigh about 1,000 pounds. Preliminary designs include a 2.7 meter (9 feet) diameter, 15 centimeter (6 inches) -thick, carbon-foam-filled solar shield atop the spacecraft body, similar to APL’s MESSENGER spacecraft.

The probe will be solar powered (no problem there!) with two sets of solar arrays that will retract or extend as the spacecraft swings toward or away from the sun during several loops around the inner solar system, making sure the panels stay at proper temperatures and power levels. At its closest passes the spacecraft must survive solar intensity more than 500 times what spacecraft experience while orbiting Earth.

“Solar Probe is a true mission of exploration,” says Dr. Robert Decker, Solar Probe project scientist at APL. “For example, the spacecraft will go close enough to the sun to watch the solar wind speed up from subsonic to supersonic, and it will fly though the birthplace of the highest energy solar particles. And, as with all missions of discovery, Solar Probe is likely to raise more questions than it answers.”

Solar Probe will use seven Venus flybys over nearly seven years to gradually shrink its orbit around the sun, coming as close as 4.1 million miles to the sun, about eight times closer than any spacecraft has come before.

The main goals of the Solar Probe are to determine the structure and dynamics of the sun’s magnetic field, trace the flow of energy that heats the corona and accelerates the solar wind, and explore dusty plasma near the sun and its influence on solar wind and energetic particle formation. This mission will also help us learn more about the sun-Earth relationship.

Original News Source: Eureka Alert

April 3, 2008December 24, 2015 by Ian O'Neill

There is No Sun-Link with Global Warming

The connection between solar activity and global warming has been a contentious issue for a long time. The idea that cosmic rays create global cloud cover just doesn’t seem to be working out; even the highest estimates of cloud cover variation caused by cosmic ray flux predict the effect to be very small. Now UK scientists have stepped into the debate, producing scientific evidence that there is no link between global warming, cosmic rays and solar activity. Sorry global warming sceptics, we might have to cut back on the emissions after all…

The connection between solar activity and global warming is thought to go like this: The Sun experiences massive changes in energy output throughout the 11-year solar cycle. At its peak (at solar maximum), the Sun’s influence over local space is at its highest. Its massive magnetic field will envelop the Earth and spiral into interplanetary space. As it does so, the immense and large-scale solar wind will deflect high energy cosmic rays. So, counter-intuitively, when the Sun is at its most active, cosmic ray collisions with the atmosphere is at its lowest. It is has been predicted by scientists such as Henrik Svensmark at the Danish National Space Center (DNSC) that these high energy cosmic rays will impact the Earth’s atmosphere, create droplets of water, thus generating cloud cover. So, following this logically, we should have a global decrease in cloud cover during periods of high solar activity (when cosmic rays are not deflected by the solar wind), causing global warming (as there will be less clouds to reflect the solar radiation). Many of the climate problems we are having at the moment can then be attributed to the Sun and not human activity.

But there’s a problem. As previously reported by the Universe Today, research groups will often publish conflicting results about the cosmic ray effect on cloud production. In one of the most definitive results to come out of this area of study has just been announced by UK scientists, and guess what? The Sun/cosmic-ray theory has no measurable effect on the climate change we are currently experiencing.

Dr. Svensmark’s idea was central to the science behind the documentary “The Great Global Warming Swindle” where the human impact on global climate change was brought into question. This theory has been under fire since its conception by highly regarded scientists such as Mike Lockwood from the UK’s Rutherford-Appleton Laboratory. Svensmark stands by his work. So with this in mind, Dr. Terry Sloan from Lancaster University set out to prove Svensmark’s hypothesis. But the results aren’t pretty.

“We tried to corroborate Svensmark’s hypothesis, but we could not […] So we had better carry on trying to cut carbon emissions.” – Dr. Terry Sloan

In a separate study, Giles Harrison from Reading University, also studied the effect of cosmic ray flux on the amount of cloud cover, stating it is an important area of research, “…as it provides an upper limit on the cosmic ray-cloud effect in global satellite cloud data“. Although restricted to the atmosphere above the UK, Harrison’s study also returns the verdict that there is only a very weak cosmic ray effect on cloud production.

The Intergovernmental Panel on Climate Change (IPCC) released a report last year pointing the finger at human activity as the root cause behind global warming. There are very strong correlations between carbon emissions and global warming since the 1970s, so the IPCC has strongly recommended that the international community make radical cuts to their carbon emissions. What’s more the IPCC point out that the contribution from greenhouse gas emissions outweighs the effect of solar variability by a factor of 13 to one.

“…as far as we can see, he has no reason to challenge the IPCC – the IPCC has got it right.” – Dr. Terry Sloan

Source: BBC

April 2, 2008December 24, 2015 by Ian O'Neill

Source of the Slow Solar Wind Found (Video)

The solar wind comes in two modes: fast and slow. Solar astronomers have a good idea as to where the fast solar wind comes from: polar coronal holes of open magnetic field lines, blasting solar particles at speeds of over 3 million km/hr. But what about the slow solar wind which fires particles into space at a pedestrian 1.5 million km/hr? We know it comes from the streamer belt above equatorial regions of the Sun, but we have never been able to look lower. But now, with the help of the Hinode observatory, stunning high-resolution images and video have been captured showing solar dynamics previously overlooked. The point at which the Sun ejects slow wind particles into space can now be studied in unparalleled detail to help us understand the dynamics of space weather and solar storms.

The Sun is a complex, magnetic body. Its magnetic field is highly dynamic, varying in activity throughout the 11-year solar cycle. We have just witnessed the Sun entering “Solar Cycle 24” (although some old sunspots from the previous cycle have just been seen) and it will gradually build in energy before reaching “solar maximum” in a few years time (looks like the solar storms will be bigger than 2003’s flare excitement).

This time of relative calm (known as “solar minimum”) allows solar physicists to study the less explosive dynamics in the lower corona (the Sun’s atmosphere), chromosphere and photosphere. It is in this region that magnetic field lines (or magnetic flux) are pushed through the photosphere and the plasma from the solar interior is guided by the magnetic flux high into the corona. These hot and bright arcs of magnetism and superheated plasma are known as coronal loops, the scene of rapid reconnection events, sometimes sparking flares and coronal mass ejections (CMEs). But this time the Hinode science team have observed a steady release of solar plasma, venting from the solar interior around a cluster of bright coronal loop footpoints. The location of this steady release of plasma forms the origin of the slow solar wind.

“It is fantastic to finally be able to pinpoint the source of the solar wind – it has been debated for many years and now we have the final piece of the jigsaw. In the future we want to be able to work out how the wind is transported through the solar system.” – Prof. Louise Harra, University College London, Mullard Space Science Laboratory.

See the Hinode video of the region generating solar wind particles…

These dazzling images were captured by the Extreme Ultraviolet Imaging Spectrometer (EIS) on board the Japanese Hinode solar observatory. The observatory, which orbits the Earth, constantly looking at the Sun, has given us unrivaled observations of the Sun in X-ray and EUV wavelengths. Launched by Japan, the project also has collaborators in the UK and US.

These new discoveries are of vast importance to us. The solar wind carries a stream of highly energetic particles from the Sun and into space. The solar wind bathes the Earth in a radioactive stream, carrying the remnants of the solar magnetic field with it. The magnetic field can interact with the Earth’s magnetic field, allowing solar particles to rain down on our Polar Regions, creating vast light displays: the Aurora. However, these particles are also highly dangerous to any unprotected astronaut or sensitive satellite orbiting our planet. It is of paramount importance that as we venture further and further into space that we forecast the characteristics of the solar wind before it hits us. These new observations will aid our understanding of the conditions at the solar wind source and greatly improve our space weather-predicting ability.

Source: ESA

April 2, 2008December 24, 2015 by Tammy Plotner

The Sun’s Magnetic Fountains

For you solar observing fans, enjoy the beauty. Over the years both the public and astronomers alike have witnessed the Sun’s volatile and ever-changing atmosphere. Before our eyes huge geysers of hot gas spew into the solar corona at tens of thousands of km per hour. Every few minutes they erupt and reach dynamic proportions. Now a team of scientists have used the Hinode spacecraft to find the origin and progenitor of these fountains – immense magnetic structures that thread through the solar atmosphere.

Today at the Royal Astronomical Society National Astronomy Meeting in Belfast (NAM 2008), team leader Dr. Michelle Murray from the Mullard Space Science Laboratory (MSSL, University College London) presented the latest results from Hinode spacecraft combined with computer emulated solar conditions. Since its launch in October 2006, scientists have been using Hinode to examine the solar atmosphere in extraordinary detail. One of it’s premier instruments is the Extreme Ultraviolet Imaging Spectrometer. The EIS generates images of the Sun and gives information on the speed of the moving gases.

At the core of the solar magnetic field, immense jets of hot gas are forced to the surface through increases in pressure. Just like an earthly geyser, when the pressure releases the gases fall back towards the Sun’s surface. But what causes the pressure? Unlike the volcanic activity that drives the terrestrial phenomena, solar fountains are caused by rearrangements of the Sun’s magnetic field, a continual process that results in looping cycles of increasing and decreasing pressure.

“EIS has observed the Sun’s fountains in unprecedented detail and it has enabled us to narrow down the fountains’ origins for the first time”, comments team member and MSSL postgraduate student Deb Baker. “We have also been able to find what drives the fountains by using computer experiments to replicate solar conditions.”

The sun-observing Hinode satellite is now in a sun-synchronous orbit, which allows it to observe the sun for uninterrupted periods lasting months at a time. Using a combination of optical, EUV and X-ray instrumentation Hinode will study the interaction between the Sun’s magnetic field and its corona to increase our understanding of the causes of solar variability.

“The computer experiments demonstrate that when a new section of magnetic field pushes through the solar surface it generates a continual cycle of fountains”, explains Dr. Murray, “but new magnetic fields are constantly emerging across the whole of the solar surface and so our results can explain a whole multitude of fountains that have been observed with Hinode.”

April 2, 2008December 24, 2015 by Nancy Atkinson

STEREO Spacecraft Captures Footage of a Solar Tsunami

A solar tsunami blasted its way through the sunâ€™s lower atmosphere on May, 19 2007, and the action was captured by the twin STEREO spacecraft. Solar tsunamis are launched by huge explosions near the Sun’s atmosphere, called coronal mass ejections (CMEs). Although solar tsunamis share much in common with tsunamis on Earth, the solar version can travel at over a million kilometers per hour. Last yearâ€™s tsunami blasted and rolled for about 35 minutes, reaching peak speeds around 20 minutes after the initial flare. The observations were made by a team from Trinity College, Dublin.

“The energy released in these explosions is phenomenal; about two billion times the annual world energy consumption in just a fraction of a second. In half an hour, we saw the tsunami cover almost the full disc of the Sun, nearly a million kilometers away from the epicenter,” said David Long, a member of the team that made the observations.

STEREO’s Extreme Ultraviolet Imager (EUVI) instruments monitor the Sun at four wavelengths which correspond to temperatures ranging between 60,000 and 2 million degrees Celsius. At the lowest of these temperatures, scientists can see structures in the chromosphere, a thin layer of the solar atmosphere that lies just above the Sun’s visible surface. At temperatures between 1 and 2 million degrees Celsius, scientist can monitor features at varying levels in the solar corona.

The SOHO spacecraft, which was launched in 1995, also monitors the Sun at these wavelengths but only took images four times per day, giving scientists rare snapshots of these tsunamis. STEREO’s EUVI instruments take an image every few minutes to create a series, making it possible for scientists to track how the wave spreads over time.

Click here for a Quicktime animation of the event.

This is the first time that a tsunami has been observed at all four wavelengths, which enabled the team to see how the wave moved through the different layers of the solar atmosphere.

“To our surprise, the tsunami seems to move with similar speed and acceleration through all the layers. As the chromosphere is much denser than the corona, we’d expect the pulse there to drag. It’s a real puzzle,” said Dr. Peter Gallagher, another member of the team.

To complicate matters, the interval between images is not the same for all four cameras. At the time of the tsunami, the cameras monitoring radiation at 1 million degrees Celsius were set to take an image every 2.5 minutes. They recorded much higher speeds and accelerations for the wave than the other cameras, which were on 10 or 20 minute cycles. By taking a sample of one image in four, the data from these cameras matched the lower values observed in the other layers.

“We’ve thought for some time that the tsunamis might be caused by magnetic shockwaves but, in previous snapshots, the waves appeared to be travelling too slowly. However, we’ve seen from this set of observations that if the time interval between images is too long, it’s easy to underestimate the speed that the waves are moving. With a few more rapid-sequence observations of solar tsunamis, we should finally be able to identify the cause of these waves,” said Gallagher.

The discovery will be presented by David Long at the RAS National Astronomy Meeting in Belfast on Wednesday April 2, 2008.

For more information and animations, see Trinity College’s pageabout the solar tsunami.

Original News Source: RAS press release