12.02.2022
Dark side of Venus revealed in new NASA photos
A NASA spacecraft has captured never-before-seen images of Venus, providing stunning views of the hellishly hot surface of the second rock from the sun.
Appearing radiant against the cosmic backdrop, the images show Venus in visible light, which is the part of the electromagnetic spectrum that the human eye can see. A detailed analysis of the images, taken of Venus' "night side," or the side facing away from the sun, was published Wednesday in the journal Geophysical Research Letters.
"The surface of Venus, even on the nightside, is about 860 degrees," Brian Wood, an astrophysicist at the U.S. Naval Research Laboratory and the study’s lead author, said in a statement. "It's so hot that the rocky surface of Venus is visibly glowing, like a piece of iron pulled from a forge."
In addition to revealing characteristics of Venus' landscape and geological makeup, the photos could help scientists understand more about Earth's neighbor and "twin," including why Venus ended up so inhospitable despite being a similar size and density to Earth.
"Venus is the third-brightest thing in the sky, but until recently we have not had much information on what the surface looked like," Wood said in the statement.
Venus' thick atmosphere and clouds of sulfuric acid typically obscure the planet's features from view, but NASA's Parker Solar Probe was able to see through the hazy shroud, down to the planet's ultra-hot surface.
NASA announces two new missions to explore Venus
JUNE 7, 202104:44The images were captured in February 2021, when the Parker Solar Probe flew past Venus and the spacecraft was able to see the planet's night side in its entirety.
The Parker Solar Probe launched in August 2018 and is designed to study the sun’s atmosphere. The probe snapped other photos of Venus during a previous flyby in July 2020. At the time, the scientists planned to use those observations to measure the speed and motions of Venus' clouds.
To their surprise, the Parker Solar Probe saw through to the planet's surface.
Last February, when the spacecraft again sailed past Venus, the astronomers trained the probe's eyes on the planet's enigmatic night side.
The resulting images were taken across a range of wavelengths, from visible light to near-infrared, which is just beyond what the human eye can detect. And when stitched together into a video, it's possible to pick out dark patches indicating cooler, higher altitude regions against the lighter, warmer lowlands.
A bright ring can also be seen around the planet, a halo of light known as "airglow" that is caused by oxygen atoms emitting light in the atmosphere.
"The images and video just blew me away," Wood said.
The researchers compared the new images to observations from NASA's Magellan spacecraft, which launched in 1989 on a mission to map the entire surface of Venus. The Parker Solar Probe's views aligned with topographical landmarks seen by the Magellan spacecraft, including the Tellus Regio plateau in the northern hemisphere of Venus and a continent-sized highland known as Aphrodite Terra.
Wood and his colleagues said the flyby images will help researchers better understand the planets in the inner solar system. Venus, Earth and Mars all formed at around the same time, but the planets diverged wildly in their evolution. While Venus' thick, heat-trapping atmosphere makes it the hottest of our solar system's planets, Mars is cold and dry and is thought to have been stripped of most of its atmosphere billions of years ago.
Insights into how Venus came to be could shape some of the upcoming missions to the planet. NASA's DAVINCI+ mission, scheduled to launch in 2029, is designed to descend through the atmosphere, analyzing its chemistry and temperature, before landing on the surface. Ahead of the DaVinci mission, in 2027, the agency is planning to launch a spacecraft named VERITAS into orbit around Venus to study its hot conditions.
The European Space Agency also has its sights set on Venus, with a probe called EnVision that is designed to sample trace gases in the planet's atmosphere. The EnVision mission is expected to launch in the early 2030s.
"By studying the surface and atmosphere of Venus, we hope the upcoming missions will help scientists understand the evolution of Venus and what was responsible for making Venus inhospitable today," Lori Glaze, director of the Planetary Science Division at NASA Headquarters, said in a statement.
Quelle: NBC News
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Update: 20.02.2023
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Instrument on NASA's Parker Solar Probe switches off unexpectedly
But the mission team expects it to come back online soon.
One of the instruments on NASA's Parker Solar Probe powered down unexpectedly last weekend, but don't panic — the mission team expects it to come back online soon.
The sun-studying spacecraft switched off its Energetic Particle Instrument-Hi (EPI-Hi) on Feb. 12, while a software patch was being uploaded to it, NASA officials explained in a brief Parker Solar Probe update on Friday (Feb. 17).
"An anomaly review board determined the instrument was turned on prematurely before the new patch was completely loaded," the update states(opens in new tab).
"The instrument will remain off for several weeks as the geometry between the probe, the sun and solar radio frequency interference will prevent a good uplink," it continues. "The EPI-Hi is expected to return to normal operations after this blackout period, before the spacecraft begins its 15th close encounter with the sun on March 12."
The Parker Solar Probe remains healthy overall, NASA officials added in the update.
The Parker Solar Probe launched atop a Delta IV Heavy rocket in August 2018 on a $1.5 billion mission to study the sun like never before.
Mission scientists aim to solve several solar mysteries, chief among them why the sun's outer atmosphere, or corona, is so much hotter than its surface and how the solar wind — the stream of charged particles flowing constantly from the sun — reaches its incredible velocities.
The Parker Solar Probe gathers most of its data during daring super-close flybys of the sun, which expose the spacecraft to sizzling temperatures and accelerate it to tremendous speeds. (Solar gravity is a powerful thing.)
These flybys occur roughly once every five months. The next one, the 15th of the mission to date, will peak on March 17(opens in new tab), when the probe zooms just 5.3 million miles (8.5 million kilometers) above the sun's surface.
As its name suggests, EPI-Hi is designed to measure high-energy solar particles. It's one of two particle detectors, along with EPI-Lo, that make up the spacecraft's Integrated Science Investigation of the Sun instrument.
The Parker Solar Probe is equipped with three other instrument suites as well — the Fields Experiment, the Wide-field Imager for Solar Probe (WISPR) and the Solar Wind Electrons Alphas and Protons investigation, or SWEAP.
Quelle: SC
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Update: 9.06.2023
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Parker Solar Probe flies into the fast solar wind and finds its source
Artist’s concept of the Parker Solar Probe spacecraft approaching the sun. Launched in 2018, the probe is increasing our ability to forecast major space-weather events that impact life on Earth. (Image credit: NASA)
Artist’s concept of the Parker Solar Probe spacecraft approaching the sun. Launched in 2018, the probe is increasing our ability to forecast major space-weather events that impact life on Earth. (Image credit: NASA)
NASA’s Parker Solar Probe has flown close enough to the sun to detect the fine structure of the solar wind close to where it is generated at the sun’s surface, revealing details that are lost as the wind exits the corona as a uniform blast of charged particles.
It’s like seeing jets of water emanating from a showerhead through the blast of water hitting you in the face.
In a paper to be published this week in the journal Nature, a team of scientists led by Stuart D. Bale, a professor of physics at the University of California, Berkeley, and James Drake of the University of Maryland-College Park, report that the Parker Solar Probe has detected streams of high-energy particles that match the supergranulation flows within coronal holes, which suggests that these are the regions where the so-called “fast” solar wind originates.
Coronal holes are areas where magnetic field lines emerge from the surface without looping back inward, thus forming open field lines that expand outward and fill most of space around the sun. These holes are usually at the poles during the sun’s quiet periods, so the fast solar wind they generate doesn’t hit Earth. But when the sun becomes active every 11 years as its magnetic field flips, these holes appear all over the surface, generating bursts of solar wind aimed directly at Earth.
Understanding how and where the solar wind originates will help predict solar storms that, while producing beautiful auroras on Earth, can also wreak havoc with satellites and the electrical grid.
“Winds carry lots of information from the sun to Earth, so understanding the mechanism behind the sun’s wind is important for practical reasons on Earth,” Drake said. “That’s going to affect our ability to understand how the sun releases energy and drives geomagnetic storms, which are a threat to our communication networks.”
A flattened map of the sun’s entire surface, or corona, imaged in extreme ultraviolet wavelengths by the NASA Solar Dynamics Observatory (SDO) satellite. The two dark regions below the middle of the image are the coronal holes sampled by the Parker Solar Probe. Within these coronal holes, flows in the solar atmosphere create intense, complex magnetic fields that annihilate and produce the pressure and energy to overcome solar gravity and send high-energy particles outward — the fast solar wind. The funnels of intense magnetic field where the fast solar wind actually originates — large convection cells called supergranulations — are not visible inside the coronal holes. (Image courtesy of NASA)
Based on the team’s analysis, the coronal holes are like showerheads, with roughly evenly spaced jets emerging from bright spots where magnetic field lines funnel into and out of the surface of the sun. The scientists argue that when oppositely directed magnetic fields pass one another in these funnels, which can be 18,000 miles across, the fields often break and reconnect, slinging charged particles out of the sun.
“The photosphere is covered by convection cells, like in a boiling pot of water, and the larger scale convection flow is called supergranulation,” Bale said. “Where these supergranulation cells meet and go downward, they drag the magnetic field in their path into this downward kind of funnel. The magnetic field becomes very intensified there because it’s just jammed. It’s kind of a scoop of magnetic field going down into a drain. And the spatial separation of those little drains, those funnels, is what we’re seeing now with solar probe data.”
Based on the presence of some extremely high-energy particles that the Parker Solar Probe has detected — particles traveling 10 to 100 times faster than the solar wind average — the researchers conclude that the wind could only be made by this process, which is called magnetic reconnection. The probe was launched in 2018 primarily to resolve two conflicting explanations for the origin of the high-energy particles that comprise the solar wind: magnetic reconnection or acceleration by plasma or Alfvén waves.
“The big conclusion is that it’s magnetic reconnection within these funnel structures that’s providing the energy source of the fast solar wind,” Bale said. “It doesn’t just come from everywhere in a coronal hole, it’s substructured within coronal holes to these supergranulation cells. It comes from these little bundles of magnetic energy that are associated with the convection flows. Our results, we think, are strong evidence that it’s reconnection that’s doing that.”
The funnel structures likely correspond to the bright jetlets that can be seen from Earth within coronal holes, as reported recently by Nour Raouafi, a co-author of the study and the Parker Solar Probe project scientist at the Applied Physics Laboratory at Johns Hopkins University. APL, located in Laurel, Maryland, designed, built, manages and operates the spacecraft.
“Solving the mystery of the solar wind has been a six-decade dream of many generations of scientists,” said Raouafi. “Now, we are grasping at the physical phenomenon that drives the solar wind at its source — the corona.”
Plunging into the sun
By the time the solar wind reaches Earth, 93 million miles from the sun, it has evolved into a homogeneous, turbulent flow of roiling magnetic fields intertwined with charged particles that interact with Earth’s own magnetic field and dump electrical energy into the upper atmosphere. This excites atoms, producing colorful auroras at the poles, but has effects that trickle down into Earth’s atmosphere. Predicting the most intense winds, called solar storms, and their near-Earth consequences is one mission of NASA’s Living With a Star program, which funded Parker.
The previous image marked with colored lines that indicate the boundaries of the open field lines (outward-pointing is red, inward-pointing is blue) as predicted by a computer model. These regions correspond well to the coronal holes in the EUV map. The white boxes show the points of origin of the magnetic field lines that the Parker Solar Probe passed through as it traveled across the sun’s surface.
The probe was designed to determine what this turbulent wind looks like where it’s generated near the sun’s surface, or photosphere, and how the wind’s charged particles — protons, electrons and heavier ions, primarily helium nuclei — are accelerated to escape the sun’s gravity.
To do this, Parker had to get closer than 25 to 30 solar radii, that is, closer than about 13 million miles.
“Once you get below that altitude, 25 or 30 solar radii or so, there’s a lot less evolution of the solar wind, and it’s more structured — you see more of the imprints of what was on the sun,” Bale said.
In 2021, Parker’s instruments recorded magnetic field switchbacks in the Alfvén waves that seemed to be associated with the regions where the solar wind is generated. By the time the probe reached about 12 solar radii from the surface of the sun — 5.2 million miles — the data were clear that the probe was passing through jets of material, rather than mere turbulence. Bale, Drake and their colleagues traced these jets back to the supergranulation cells in the photosphere, where magnetic fields bunch up and funnel into the sun.
But were the charged particles being accelerated in these funnels by magnetic reconnection, which would slingshot particles outward, or by waves of hot plasma — ionized particles and magnetic field — streaming out of the sun, as if they’re surfing a wave?
The fact that Parker detected extremely high-energy particles in these jets — tens to hundreds of kiloelectron volts (keV), versus a few keV for most solar wind particles — told Bale that it has to be magnetic reconnection that accelerates the particles and generates the Alfvén waves, which likely give the particles an extra boost.
“Our interpretation is that these jets of reconnection outflow excite Alfvén waves as they propagate out,” Bale said. “That’s an observation that’s well known from Earth’s magnetotail, as well, where you have similar kind of processes. I don’t understand how wave damping can produce these hot particles up to hundreds of keV, whereas it comes naturally out of the reconnection process. And we see it in our simulations, too. ”
The Parker Solar Probe won’t be able to get any closer to the sun than about 8.8 solar radii above the surface — about 4 million miles — without frying its instruments. Bale expects to solidify the team’s conclusions with data from that altitude, though the sun is now entering solar maximum, when activity becomes much more chaotic and may obscure the processes the scientists are trying to view.
“There was some consternation at the beginning of the solar probe mission that we’re going to launch this thing right into the quietest, most dull part of the solar cycle,” Bale said. “But I think without that, we would never have understood this. It would have been just too messy. I think we’re lucky that we launched it in the solar minimum.”
Quelle: Berkeley UNIVERSITY OF CALIFORNIA
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Update: 15.06.2023
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PARKER SOLAR PROBE DETECTS SOURCE OF SOLAR WIND
The Sun flings charged particles and accompanying magnetic fields into the solar system, but how? NASA’s Parker Solar Probe dives in to find out.
The dark area across the top of the sun in this image is a coronal hole, a region on the Sun where the magnetic field is open to interplanetary space. (The hole appears dark in this ultraviolet image because the plasma is sparse and thus cooler.) Plasma in these regions accelerates into a fast solar wind, but how this happens has remained an open question.
NASA / SDO
The solar wind — the flow of charged particles, or plasma, from the Sun — radiates out over all the bodies in the solar system, forming a vast, Sun-centered bubble in the dark void of space. It’s essential to life on Earth, but it also stirs up geomagnetic storms that produce power cuts, aurorae, and other earthly disturbances. The mechanism by which the solar wind arises is still not fully understood, so a team of researchers led by Stuart Bale (University of California, Berkeley) set out to tackle the quandary.
The team, whose findings are published in Nature, drew on data collected by NASA’s Parker Solar Probe. Since it launched in 2018, Parker has been circling the Sun in a series of gradually shrinking orbits that are bringing it closer to the solar surface than any previous human-made object.
Indeed, Parker has even dipped into the Sun’s atmosphere, or corona, flying as close as 5.3 million miles to the Sun’s visible surface, or photosphere, which is covered in boiling “bubbles” called granules as well as larger-scale patterns called supergranules.
On the Sun's visible surface, or photosphere, heating plasma rises in the bright, convective “bubbles” (granules) then cools and falls into the dark lanes between the granules.
Image Credit: NSF/AURA/NSO Image Processing: Friedrich Wöger(NSO), Catherine Fischer (NSO)
Supergranules are similar to granules but on much larger scales (about 35,000 km across). They're best seen in measurements of the "Doppler shift" where light from material moving toward us is shifted to the blue while light from material moving away from us is shifted to the red. These bulk, boiling-type motions occur over the entire Sun and hold the key to understanding the fast solar wind.
NASA Marshall Space Flight Center / D. Hathaway
Parker was deployed to answer what accelerates the plasma and accompanying magnetic fields that launch off the photosphere and into the corona. This solar wind travels at different speeds, fast and slow. While both speeds of wind are linked to magnetism in the Sun’s atmosphere, each has its own source. There’s a broad consensus that the fast solar wind originates in coronal holes, regions where the Sun’s magnetic field lines are effectively “open,” extending far into interplanetary space before looping back in.
Over a coronal hole (here, the dark region near the center of the image) are open to interplanetary space, allowing accelerated to flow fast and furious, at speeds up to 800 km/s (2 million mph).
SDO/ AIA / Veronig A. & Temmer M. (University of Graz, Austria)
But what happens in these open fields to drive the solar wind? There are two competing theories. It could be either magnetic waves known as Alfvén waves, which pass through plasma, or magnetic reconnection. Both processes are known to take place on the Sun.
The researchers analyzed a range of measurements taken by Parker in November 2021, during its 10th perihelion, when it passed close to the Sun. The probe measured the solar wind’s plasma density and energy, as well as its magnetic field strength. The team combined these data with surface magnetic field measurements from the Solar Dynamics Observatory, a separate surveyor that launched in 2010.
The team saw that Parker was buffeted during its encounter by microstreams — short, jet-like bursts of high-speed solar wind. With the help of computer simulations, the team established that these microstreams are likely driven by reconnection.
According to the reconnection hypothesis, plasma is accelerated off the surface of the Sun by magnetic reconnection within the coronal holes, specifically in the regions between the supergranules.
“Where these supergranulation cells meet and go downward, they drag the magnetic field in their path into this downward kind of funnel,” Bale says. “The magnetic field becomes very intensified there because it's just jammed.”
This diagram shows the reorganization of magnetic fields by a process called magnetic reconnection. Here, two opposing magnetic field lines meet (A), connecting at the point where they would cross (B), and then sending a burst of particles accelerating outward accompanied by an S-shape twist in the magnetic field (C). Parker sees the S-shape twist as a magnetic switchback.
Gregg Dinderman / S&T; source: Justin Kasper / Levi Hutmacher / University of Michigan Engineering
As the funnels pull in neighboring magnetic fields, the fields reconnect, releasing magnetic energy. Microstreams of sped-up plasma are spewed out into space, along with associated sudden changes in magnetic field direction known as switchbacks. These bursts of solar wind are what hit the spacecraft.
The researchers showed this by linking the bursts and switchbacks to their footprints in two coronal holes. They also estimated the rate at which magnetic energy was released in the reconnection events and found that it was equivalent to that required to power the fast solar wind flows. In addition, they measured unusually high-energy particles in the jets, which point to the involvement of magnetic reconnection.
As the Parker Solar Probe flies over a coronal hole (shown here in white on the Sun's surface), it encounters switchback magnetic fields as well as small, speedy bursts of solar wind.
University of California, Berkeley; spacecraft image: NASA / Johns Hopkins APL
Alfvén waves, under this interpretation, are an effect of reconnection. As jets of reconnection-accelerated plasma gush out of the coronal holes, they may produce Alfvén waves. These waves may in turn boost the solar wind, but they are not the primary driver of it.
Michael Hahn (Columbia University), who wasn’t involved in the study, finds the evidence “convincing”. But understanding precisely how reconnecting magnetic fields heat and accelerate plasma remains an open question, he points out.
“The authors favor an explanation that the reconnection directly heats the plasma close to the Sun,” Hahn says. But he explains that another option mentioned in the study, indirect transfer of energy, is also possible. First, the energy goes into magnetic waves in the plasma or into turbulence, and only later, farther away from the Sun, does that energy transfer to the plasma.
The myriad of energy-generating processes taking place in the corona makes it complex to identify which are the most significant, Hahn adds. This complexity presents a challenge for solar physicists to overcome.
By broadening the evidence base and bolstering the case for magnetic reconnection fueling the fast solar wind, the Nature study opens up future avenues of inquiry, such as an investigation into how much of the energy generated by reconnection is transferred into turbulence. It also paves the way for improved prediction of geomagnetic storms. Far from being the end of the matter, it represents but the latest development in an ongoing discussion.
Quelle: Sky&Telescope
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Update: 12.08.2023
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NASA's Parker Solar Probe to make closest flyby of Venus on Aug. 21
If all goes well, the spacecraft will soon be headed even closer to the sun
An artist's depiction of NASA's Parker Solar Probe flying past Venus. (Image credit: NASA/Johns Hopkins APL/Steve Gribben
Since 2021, NASA's Parker Solar Probe has been treading impressively close to the sun in order to capture unprecedented data about our home star.
In fact, the record-breaking spacecraft completed its closest approach yet to the blazing ball of plasma in June, coming within just 5.3 million miles (8.3 million kilometers) of the solar surface. To reach these incredible milestones, Parker gets by with a little help from its friends. Well, one friend: Venus.
NASA says Parker is on track to make its sixth and closest flyby of Venus on Aug. 21, thanks to some precise maneuvering that took place on Aug. 3. The goal is for the probe to use the amber-hued planet's gravity to tighten its orbit around the sun — a technique Parker has been employing repeatedly during its mission, which began with a launch on Aug. 12, 2018. If all goes well with this Venusian approach, Parker will come within about 4.5 million miles (7.2 million km) of the solar surface on Sept. 27.
But the story won't end there.
NASA has one more Venus flyby planned after this one, which is designed to sling Parker to within just 3.9 million miles (6.2 million km) of the sun. For context, Earth sits about 93 million miles (149 million km) from that shining yellow orb. So, Parker's going to get really, really close.
To delve into some technical details, Parker's recent maneuvering consisted of the craft firing its small thrusters for 4.5 seconds in order to adjust its trajectory by 77 miles (124 kilometers) and increase its speed by 1.4 seconds while heading to Venus. These shifts are actually quite minute considering the probe has been traveling at hundreds of thousands of miles per hour while flying through the inner solar system.
During September's upcoming solar approach, for instance, the team says Parker will be moving at 394,742 mph (635,276 kph) — a new speed record for the probe and for spacecraft in general. And at its closest approach ever, it's expected that Parker will zoom through space at about 430,000 mph (700,000 kph) — a velocity NASA says would be fast enough to get you from Philadelphia to Washington, D.C. in one single second.
"Parker’s velocity is about 8.7 miles per second, so in terms of changing the spacecraft’s speed and direction, this trajectory correction maneuver may seem insignificant," Yanping Guo, mission design and navigation manager at the Johns Hopkins Applied Physics Laboratory in Maryland, said in a statement. "However, the maneuver is critical to get us the desired gravity assist at Venus, which will significantly change Parker’s speed and distance to the sun."
Since its launch in 2018, Parker has been dubbed the probe that'll "touch the sun." And that it did. In 2021, it finally flewthrough our star's upper atmosphere, otherwise known as the corona, which officially meant it truly "touched the sun."
With Parker's data, scientists hope to answer several big questions about our star, such as why the corona is so much hotter than the surface – what a weird conundrum – and decode the ins and outs of the stream of charged particles known as the solar wind. And, that's just the beginning. Eventually, perhaps it'll solve a few riddles we didn't quite know we should be pondering.
After all, it was only recently when scientists found the sun blasting out the highest-energy radiation ever recorded, suggesting that we just may not have this star figured out yet.
Quelle: SC
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Update: 18.09.2023
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Parker Observes Powerful Coronal Mass Ejection ‘Vacuum Up’ Interplanetary Dust
On Sept. 5, 2022, NASA’s Parker Solar Probe soared gracefully through one of the most powerful coronal mass ejections (CMEs) ever recorded – not only an impressive feat of engineering, but a huge boon for the scientific community. Parker’s journey through the CME is helping to prove a 20-year-old theory about the interaction of CMEs with interplanetary dust, with implications for space weather predictions. The results were recently published in The Astrophysical Journal.
A 2003 paper theorized that CMEs may interact with interplanetary dust in orbit around our star and even carry the dust outward. CMEs are immense eruptions from the Sun’s outer atmosphere, or corona, that help drive space weather, which can endanger satellites, disrupt communications and navigation technologies, and even knock out power grids on Earth. Learning more about how these events interact with interplanetary dust could help scientists better predict how quickly CMEs could travel from the Sun to Earth, forecasting when the planet could see their impact.
Parker has now observed this phenomenon for the first time.
“These interactions between CMEs and dust were theorized two decades ago, but had not been observed until Parker Solar Probe viewed a CME act like a vacuum cleaner, clearing the dust out of its path,” said Guillermo Stenborg, an astrophysicist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and lead author on the paper. APL built and operates the spacecraft.
This dust is made up of tiny particles from asteroids, comets, and even planets, and is present throughout the solar system. A type of faint glow called zodiacal light, sometimes visible before sunrise or after sunset, is one manifestation of the cloud of interplanetary dust.
The CME displaced the dust all the way out to about 6 million miles from the Sun – about one-sixth of the distance between the Sun and Mercury – but it was replenished almost immediately by the interplanetary dust floating through the solar system.
In-situ observations from Parker were critical to this discovery, because characterizing dust dynamics in the wake of CMEs is challenging from a distance. According to the researchers, Parker’s observations could also provide insight into related phenomena lower down in the corona, such as coronal dimming caused by low-density areas in the corona that often appear after CMEs erupt.
Scientists observed the interaction between the CME and dust as decreased brightness in images from Parker’s Wide-field Imager for Solar Probe (WISPR) camera. This is because interplanetary dust reflects light, amplifying brightness where the dust is present.
Credit: NASA/Johns Hopkins APL/Naval Research Lab
To locate this occurrence of decreased brightness, the team had to compute the average background brightness of WISPR images across several similar orbits – sifting out normal brightness variations that occur due to solar streamers and other changes in the solar corona.
“Parker has orbited the Sun four times at the same distance, allowing us to compare data from one pass to the next very well,” Stenborg said. “By removing brightness variations due to coronal shifts and other phenomena, we were able to isolate the variations caused by dust depletion.”
Because scientists have only observed this effect in connection with the Sept. 5 event, Stenborg and the team theorize that dust depletion may only occur with the most powerful CMEs.
Nevertheless, studying the physics behind this interaction may have implications for space weather prediction. Scientists are just starting to understand that interplanetary dust affects the shape and speed of a CME. But more studies are needed to understand these interactions better.
Parker completed its sixth Venus flyby, using the planet’s gravity to sling itself even closer to the Sun for its next five close approaches. This occurs as the Sun itself is approaching solar maximum, the period in the Sun’s 11-year cycle when sunspots and solar activity are most abundant. As the Sun’s activity increases, scientists hope to have the opportunity to see more of these rare phenomena and explore how they might affect our Earth environment and the interplanetary medium.
Parker Solar Probe was developed as part of NASA’s Living With a Star program to explore aspects of the Sun-Earth system that directly affect life and society. The Living With a Star program is managed by the agency’s Goddard Space Flight Center in Greenbelt, Maryland, for NASA’s Science Mission Directorate in Washington. APL designed, built, and operates the spacecraft and manages the mission for NASA.
Quelle: NASA