Tag Archives: solar wind

NASA’s Parker Solar Probe Could Help Solve One of the Mysteries of Our Sun

Artist rendering of NASA's Parker Solar Probe observing the sun. Credit: NASA/Wikimedia Commons.

Artist rendering of NASA’s Parker Solar Probe observing the sun. Credit: NASA/Wikimedia Commons.

One of the most logically-baffling solar mysteries is the fact that the sun’s surface is close to 10,000 degrees Fahrenheit while its outer atmosphere is several million degrees hotter. The body of the heat’s source itself is cooler than the atmosphere surrounding the fireball — and that’s simply against the common sense of physics.

Some physicists think that the terrific, intense heat displayed in the outer limits of the sun’s atmosphere may be explained by magnetic waves traveling to and from the solar surface, bouncing off the upper atmosphere (otherwise known as the corona) of the star. Recent studies have suggested that this activity could be tied to the sun’s zone of preferential ion heating. In this zone, ions reach scorching temperatures exceeding those at the very core of the sun.

Another element which has a role to play in this outlying solar vortex are Alfven waves. These waves are low-frequency oscillations traveling through a plasma in a magnetic field. Scientists think that these waves are making solar wind particles to collide and ricochet off one another. But once it hits the outskirts of the zone of preferential heating, the solar wind sweeps by at an extremely fast pace. Thus, it manages to evade the Alfven waves from there on out.

Researchers at trying to definitively mark the extent to which the superheating effect reaches beyond the sun. Recent research has brought light to a connection between the Alfven point (the point of altitude beyond the solar surface that permits solar wind particles to break free of the sun) and the outskirts of the zone of preferential heating. These two fields have fluctuated in unison. They shall continue their dance, and in 2021, NASA’s Parker Solar Probe, christened in honor of physicist Eugene Parker, should come in contact with the two boundaries.

The spacecraft includes instruments capable of recording a number of significant data pertaining to those solar fields. The information it would collect in some two years to come would be invaluable in this particular study.

The Parker Solar Probe was launched in August 2018. It made its second successful fly-by of our sun in early April with the follow-up perihelion (the point at which it gets closest to the sun) scheduled to occur on September 1. Visit NASA’s page on the Parker Solar Probe to learn more about it and its mission. To learn of interesting updates, check out the website of Parker Solar Probe Science Gateway.

NASA Voyager.

Voyager 2 enters interstellar space

To boldly go where just one has gone before.

Voyager probe.

Artist’s impression of Voyager in flight.
Image credits NASA / JPL.

The second member of the Voyager space probe family is emigrating from our solar system. Voyager 2 has exited the heliosphere — the limit of the Sun’s magnetic and plasma fields — back on November 5th, reported members of NASA’s Voyager team yesterday at the 2018 American Geophysical Union (AGU) fall meeting in Washington.

Voyaging

The craft is now over 11 billion miles away from Earth. Ground control says, based on sensor readings, that the craft exited the heliosphere around November 5th this year. The most compelling evidence comes from the craft’s onboard Plasma Science Experiment (PLS), NASA reports, a device that picks up on electrical currents in plasma to determine the speed, density, temperature, pressure, and flux of stellar wind in its area.

Up to now, the instrument primarily picked up on such winds (which are emissions of charged particles) generated by the Sun. Since Nov. 5th, however, it has recorded a steep decline in solar wind particles. Today, there’s no observable solar wind flow around Voyager 2, the team reports, making it overwhelmingly likely that it exited the heliosphere. Readings from three other onboard instruments — the cosmic ray subsystem, the low energy charged particle instrument, and a magnetometer — also support this conclusion.

NASA Voyager.

Illustration showing the positions of the Voyager probes outside the heliosphere.

To give you an idea of the distances involved here, keep in mind that it takes light from the Sun about 8 minutes to reach Earth. It takes roughly 16.5 hours to transmit a message from us to Voyager 2 (radio waves also travel at light-speed) at its current position.

That’s an impressive distance, but it’s not the longest trek our machines have ever pulled off — it’s the second longest. Voyager 2 follows its twin Voyager 1, which exited the heliosphere in 2012.

The heliosphere’s outer boundary, known as the heliopause, is the point at which solar winds lose their oomph and start mixing with the cold stuff of space (or, in science-speak, the “interstellar medium”). The team is excited that Voyager 2 is passing through, as it will provide first-of-their-kind readings from this exotic span of space. The probe still has a working PLS device onboard, while Voyager 1’s equivalent malfunctioned before it reached the heliopause.

Still, there’s a wealth of data to analyze already, and NASA researchers are very keen on better understanding the environment that Voyager 2 finds itself in currently.

“There is still a lot to learn about the region of interstellar space immediately beyond the heliopause,” said Ed Stone, Voyager project scientist based at Caltech in Pasadena, California.

“Voyager has a very special place for us in our heliophysics fleet,” said Nicola Fox, director of the Heliophysics Division at NASA Headquarters. “Our studies start at the Sun and extend out to everything the solar wind touches. To have the Voyagers sending back information about the edge of the Sun’s influence gives us an unprecedented glimpse of truly uncharted territory.”

Both probes have left the heliosphere but not the solar system. That boundary is considered to be the outer edge of the Oort Cloud, a bunch of small bodies still under the influence of the Sun’s gravity well. We don’t know exactly how wide the Cloud is, but it’s estimated Voyager would need some 30,000 years to fly through it. So don’t hold your breath on that one.

The Voyagers draw power from a radioisotope thermal generator (RTG), a device that relies on the nuclear decay of certain atomic species. Its output declines by around 4 watts each year. Several instruments aboard the Voyagers have been turned off over time to manage this diminishing power supply — but the RTGs won’t be able to deliver power indefinitely. Both crafts will run out of juice long before they exit the solar system.

 

Atmospheric pressure on Mars is just 1% that found on Earth. Credit: YouTube.

Martian atmosphere is not threatened by solar wind

Atmospheric pressure on Mars is just 1% that found on Earth. Credit: YouTube.

Atmospheric pressure on Mars is just 1% that found on Earth. Credit: YouTube.

In many respects, Mars is but a shell of its former self. About 3-4 billion years ago, it boasted a hot climate that could sustain an active hydrological cycle. There were heavy rains, rivers of flowing waters, even vast oceans. All of these require a thick atmosphere. Today, however, the atmosphere is roughly 100 times less dense than Earth’s, and the Red Planet is still continuously losing gas — expending about 100 grams of its atmosphere into outer space every second.

Solar wind is regarded as an important factor that can explain this atmospheric loss. However, a grad student at Luleå University of Technology, Sweden, has come to results that say otherwise. According to Robin Ramstad, who studied for his Master of Science degree in Engineering Physics at the university, Mars’ atmosphere is adequately protected from the effects of solar wind despite lacking an Earth-like magnetic dipole.

Thin air

Here on Earth, the motion of molten iron alloys in the planet’s outer core acts like a geodynamo which generates a massive magnetic field. Scientists call our planet’s magnetic field the magnetosphere. It extends for several tens of thousands of kilometers into space, well above the atmosphere, sheltering the planet from the charged particles of solar winds and cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects the Earth from harmful ultraviolet radiation.

Earth isn’t unique in this respect. Jupiter has masses of liquid metallic hydrogen in its outer mantle, creating the largest planetary magnetic field in the solar system. Uranus generates a global magnetosphere closer to the surface, which leads to some very strange quadrupole field effects —  rather than just a north and a south, there are another two poles lurking in a quadrupole field. Mars also used to have a magnetic field but lost it half a billion years after its formation.

Artist impression of Mars covered in a primitive ocean. Credit: NASA/GSFC.

Artist impression of Mars covered in a primitive ocean. Credit: NASA/GSFC.

Solar wind is a stream of charged particles released from the upper atmosphere of the Sun. First described as a phenomenon in 1859, it has been observed only in the 1960s. According to one mainstream theory, it’s also responsible for the erosion of the early Martian atmosphere, which caused the greenhouse effect to collapse on the planet. At the same time, solar wind interacts with the ionized upper atmosphere, called the ionosphere, and induces a magnetosphere.

“It has long been thought that this induced magnetosphere is insufficient to protect the Martian atmosphere,” says Robin Ramstad. “However our measurements show something different.”

Left: Charged particles from the sun (the solar wind) form an induced magnetosphere round Mars, which unlike the sun does not have its own intrinsic magnetic field (artwork: Anastasia Grigoryeva) Larger file
Right: Robin Ramstad points out the position of the Swedish instrument ASPERA-3 on a model of the Mars Express spacecraft (photo: Anastasia Grigoryeva)

Ramstad studied data beamed back to Earth by the Mars Express orbiter. The spacecraft has an ion mass analyzer mounted that measured ion escape from Mars since 2004.

The researcher combined and compared measurements of the ion escape under varying solar wind conditions and levels of ionizing solar radiation. His results suggest that solar wind has an effect on the ion escape rate, but it’s rather negligible. Instead, the ion escape rate is more dependent on EUV (extreme ultraviolet) radiation which has a large effect on the total amount of escaped atmosphere.

“Despite stronger solar wind and EUV-radiation levels under the early Sun, ion escape can not explain more than 0.006 bar of atmospheric pressure lost over the course of 3.9 billion years,” said Ramstad in a statement. “Even our upper estimate, 0.01 bar, is an insignificant amount in comparison to the atmosphere required to maintain a sufficiently strong greenhouse effect, about 1 bar or more according to climate models.”

According to Ramstad, what solar wind mainly does is it accelerates particles that are already escaping the planet’s gravity. It does not, however, increase the ion escape rate.

If Ramstad is indeed correct the question of where all of Mars’ water has gone will be put back into the scientific limelight.

Earth’s oxygen has been emigrating to the Moon for billions of years, study finds

Earth has been outsourcing oxygen to the Moon behind our back for billions of years now, a new study has found.

Image credits Junior Peres Junior / Pixabay.

The fact that Earth is leaking atmosphere doesn’t come as a surprise. We’ve known that roughly 90 metric tons of gas (out of the 5 quadrillion metric ton total) escape to outer space each day for some time now. This happens because the fringe layers of our atmosphere are made up of charged particles moving fast enough to escape gravity’s pull — kind of like natural, gaseous rockets. Even more, the planet’s magnetic field can interact with these atoms to give them an extra boost of speed. The atoms then stay in the magnetosphere — a tear-drop region of space around Earth — for a while until solar winds blast them into the void.

But a part of our atmosphere just wants to resettle, it seems.

Shoot for the moon

For the most part, the Moon is sand-blasted with high-speed jets of charged ions belching forth from the Sun as solar winds. But for 5 days each month, when our planet’s magnetosphere gets in the way and shields the moon from these particles, slower-moving atoms flow between us and our satellite. This way, an estimated 4 trillion trillion trillion atoms of oxygen have emigrated from Earth to settle in the lunar soil over the last 2,4 billion years or so.

Back in 2008, Japan’s Kaguya moon-orbiting probe picked up a dramatic change in the nature of oxygen ions traveling around the craft. They were slower than typical solar winds, and were missing a single electron.

Over time, it became clear that this change was cyclical, lasting for a short period each month. It coincided with the 5-day period when Earth’s magnetosphere shielded the Moon from solar winds. Considering this and the nature of the oxygen atoms in question, as well as their speed, they’re almost guaranteed to come from Earth, says a team led by Kentaro Terada, a cosmochemist at Osaka University in Toyonaka, Japan.

They believe that these oxygen ions originate in the ozone layer, where sunlight breaks apart the gas (O3) into regular oxygen molecules and single atoms. The gas then rises slowly and is blown out into space by solar winds. This mechanism would explain why some lunar soil samples Apollo astronauts brought back from the Moon have higher concentrations of oxygen-17 and 18 isotopes than we would have expected — the dominant form of this element in the universe is oxygen-16. Terada and his colleagues point out that the ozone layer is also disproportionately rich in these two isotopes.

Up to now, nobody has been able to explain how these anomalies formed in the lunar soil.

The findings could help researchers better understand how the Earth and Moon interact, as well as allowing better models of how particles behave in the upper atmosphere and nearby space.

The full paper “Biogenic oxygen from Earth transported to the Moon by a wind of magnetospheric ions” has been published in the journal Nature Astronomy.

NASA announcement: Martian atmosphere was stripped by solar wind

As we were hyping it a couple of days ago, NASA came up with a very interesting announcement – they figured out what transformed Mars from a watery, lush environment to the red desert we see today.

Artist’s rendering of a solar storm hitting Mars and stripping ions from the planet’s upper atmosphere.
Credits: NASA/GSFC

Astronomers have found tantalizing clues regarding the Martian past – there is now a growing consensus that Mars was, at one point in its past, able to support liquid water, protected by its atmosphere. But its atmosphere is now almost gone, only a thin blanket remaining – so what happened? Apparently, the culprit is the solar wind.

Unlike Earth, Mars lacks a global magnetic field to deflect the stream of charged particles continuously blowing off the Sun. Instead, the solar wind crashes into the Mars upper atmosphere and can accelerate ions into space

“Mars appears to have had a thick atmosphere warm enough to support liquid water which is a key ingredient and medium for life as we currently know it,” said John Grunsfeld, astronaut and associate administrator for the NASA Science Mission Directorate in Washington. “Understanding what happened to the Mars atmosphere will inform our knowledge of the dynamics and evolution of any planetary atmosphere. Learning what can cause changes to a planet’s environment from one that could host microbes at the surface to one that doesn’t is important to know, and is a key question that is being addressed in NASA’s journey to Mars.”

MAVEN was launched in November 2013, and its main mission is studying the planet’s upper atmosphere, ionosphere and interactions with the sun and solar wind. MAVEN indicates that solar wind strips away gas at a rate of about 100 grams (equivalent to roughly 1/4 pound) every second, and this actually wiped out the Martian atmosphere.

“Like the theft of a few coins from a cash register every day, the loss becomes significant over time,” said Bruce Jakosky, MAVEN principal investigator at the University of Colorado, Boulder. “We’ve seen that the atmospheric erosion increases significantly during solar storms, so we think the loss rate was much higher billions of years ago when the sun was young and more active.”

The solar wind is a stream of charged particles released from the upper atmosphere of the Sun. This plasma consists mostly of electrons and protons at speeds as high as 900 km/s and at a temperature of 1 million degrees (Celsius). Here’s an artistic representation of how this works, via NASA:

But it wasn’t just bit by bit that moved the mountain – a series of dramatic solar storms hit Mars’ atmosphere in March 2015, and MAVEN found that the loss was accelerated. This likely happened several times in the past, and it seems reasonable that several extreme events greatly accelerated the process.

“Solar-wind erosion is an important mechanism for atmospheric loss, and was important enough to account for significant change in the Martian climate,” said Joe Grebowsky, MAVEN project scientist from NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “MAVEN also is studying other loss processes — such as loss due to impact of ions or escape of hydrogen atoms — and these will only increase the importance of atmospheric escape.”

The ultimate goal of the mission is to quantify how much of the atmosphere and the water on the planet was lost in space due to solar wind.

Rosetta mission discovers the comet that “sings”

The Rosetta probe found a comet which “sings”. Image via ABC.

As I am writing this, the Rosetta mission’s lander, Philae, is mid way through its landing on a comet. If everything works out, this will be the first time humans have landed anything on a comet and will provide valuable information about not only the comet in particular, but also our solar system in general.

*UPDATE* Rosetta’s final ‘go’ has been given, the landing attempt will start today in just a few minutes!

But as Rosetta was zooming in on its destination, machines picked up a very strange signal coming from Comet 67P/Churyumov-Gerasimenko. Through some kind of interaction in the comet’s environment, 67P’s weak magnetic field seems to be oscillating at low frequencies. Scientists amplified the frequencies 10,000 times to make them audible for the human ear.


It’s still not clear exactly why this “singing” is happening, but researchers believe the oscillations may be driven by the ionisation of neutral particles from the comet’s jets. Basically, the comet’s nucleus and coma are surrounded by jets of vapor and dust which interact with the solar wind – a stream of plasma released from the upper atmosphere of the Sun, consisting mostly of electrons and protons.

As they are released into space, these particles become ionized, and because they are ionized, they interact with the comet’s magnetic field, causing the oscillations we have now picked up. But before a definitive answer is given, more research is needed.

“This is exciting because it is completely new to us,” says Karl-Heinz Glaßmeier, head of Space Physics and Space Sensorics at the Technische Universität Braunschweig, Germany. “We did not expect this and we are still working to understand the physics of what is happening.”

Hopefully, the mission will work out as planned and the lander will be successful in making its way on the surface of the comet. We’ll keep you posted!

Cassini sheds light on cosmic particle accelerators

During a chance encounter with an unusually strong blast of solar wind at Saturn, NASA’s Cassini spacecraft detected particles being accelerated to ultra-high energies (like those at the LHC); this acceleration is similar to that which takes place around distant supernovas and provides a valuable in-situ study environment.

cassini saturn

The Cassini spacecraft is an absolutely stunning evergreen source of information. Since we can’t exactly travel to distant supernovas and study this phenomena up close, the spacecraft provided a unique opportunity to observe this phenomenon up-close. The findings, published this week in the journal Nature Physics, confirm that certain kinds of shocks can become considerably more effective electron accelerators than previously thought.

Shockwaves are probably more common in space than you’d expect. The aftermath of a stellar explosion, for example, creates a huge shockwave accelerating the debris outward, just like the flow of particles from the sun (the solar wind) does when it reaches the magnetic field of a planet, forming a bow shock. Depending on the magnetic orientation and the strength of the shock, particles can be accelerated to close to the speed of light at these boundaries. These may actually be the dominant source of cosmic rays, high-energy particles that pervade our galaxy.

Researchers are most interested in what they call “quasi-parallel” shocks: where the magnetic field and the “forward”-facing direction of the shock are almost aligned – a good example of this is in supernova remnants. In this new study, Adam Masters of the Institute of Space and Astronautical Science, Sagamihara, Japan, describes the first detection of significant acceleration of electrons in a quasi-parallel shock at Saturn, coinciding with what may very well be the strongest shock ever encountered by researchers at the planet.

“Cassini has essentially given us the capability of studying the nature of a supernova shock in situ in our own solar system, bridging the gap to distant high-energy astrophysical phenomena that are usually only studied remotely,” said Masters.

Interestingly enough, this could provide useful information for particle physics, providing once again an example how phenomenas taking place at the largest of scales are tightly connected to those taking place in the subatomic universe.

Via NASA

Electric Solar Wind Sail to Power Future Space Travel In Solar System

solar windTwo years ago, the Finnish Meteorological Institute made public the fact that they had created an electric solar wind sail. Now, scientists believe that this kind of propulsion could benefit space travel significantly, throughout the Solar System.

Doctor Pekka Janhunen who invented the sail, believes it could revolutionise travelling in space, as using solar winds for thrust requires no fuel or propellant. The solar wind is a continuous plasma stream emanating from the Sun.

“We haven’t encountered major problems in any of the technical fields thus far. This has already enabled us to start planning the first test mission,” says Dr. Pekka Janhunen.

They have also developed some new techniques of welding that allow them to have spinoff applications outside the electric sail.

“The electric sail might lower the cost of all space activities and thereby, for example, help making large solar power satellites a viable option for clean electricity production. Solar power satellites orbiting in the permanent sunshine of space could transmit electric power to Earth by microwaves without interruptions. Continuous power would be a major benefit compared to, e.g. ground-based solar power where storing the energy over night, cloudy weather and winter are tricky issues, especially here in the far North,” says Dr. Pekka Janhunen.