A brand new groundbreaking measurement made by the Solar Orbiter spacecraft and the Parker Solar probe brings scientists closer than ever to solving a longstanding mystery surrounding the sun. Oddly enough, our host star’s atmosphere, or corona, is staggeringly hotter than the solar surface despite being further away from the plain source of the sun’s heat — and it is a puzzle that has troubled physicists for about 65 years.
The collaboration between these two instruments was made possible when the Solar Orbiter, operated by the European Space Agency (ESA) performed some space-based gymnastics. These maneuvers allowed the spacecraft to watch the sun and NASA’s Parker Solar Probe at the identical time. Ultimately, that allowed for simultaneous solar observations between the 2, which together indicated that turbulence is probably going heating the solar corona to incredible temperatures.
“The flexibility to make use of each Solar Orbiter and Parker Solar Probe has really opened up a wholly recent dimension on this research,” Gary Zank, co-author of a study on the outcomes and a researcher on the University of Alabama in Huntsville, said in a press release.
This team-up could finally solve the so-called “coronal heating mystery,” which revolves around that heat discrepancy between the corona, fabricated from wispy and nebulous electrically charged gas called plasma, and the sun’s surface, or photosphere.
Related: Scientists may finally know why the sun’s outer atmosphere is so freakishly hot
What’s the coronal heating mystery?
The corona can reach temperatures as great as 1.8 million degrees Fahrenheit (1,000,000 degrees Celsius), while 1,000 miles below it, the photosphere only reaches temperatures of around 10,800 degrees Fahrenheit (6,000 degrees Celsius).
That could be a troubling fact since the sun’s core, where the nuclear fusion of hydrogen to helium occurs, is where the overwhelming majority of the sun’s heat comes from. That is like air about one foot above a campfire being hotter than air one inch away from the flames.
The discrepancy in heat also means there have to be one other heating mechanism at play directly on the corona. Until now, that mechanism has evaded scientists, but turbulence within the atmosphere of the sun significantly heating coronal plasma has long been considered a plausible explanation. Nonetheless, that hypothesis had been inconceivable to analyze with data from one spacecraft.
Satellites can investigate the sun in two ways: they will rise up close and private, making in-situ measurements like NASA’s Parker Solar Probe does, or they will make more distant investigations just like the Solar Orbiter. The Solar Orbiter studies the corona from around 26 million miles (42 million kilometers) away from the sun, while the Parker Solar Probe braves the blazing hot plasma of the sun because it passes around 4 million miles (6.4 million km) from the solar surface.
But, there’s a trade-off between the 2 approaches.
Distant sensing can see broad details in regards to the sun, but suffers relating to making observations of what physics is at play in coronal plasma. However, in-situ observations can measure that plasma in greater detail but are inclined to miss the larger solar picture.
Meaning uniting the large-scale measurements of events on the sun from the Solar Orbiter with the detailed observations of the identical phenomenon by the Parker Solar Probe could present us with the full picture of the sun with all intricate details filled in — one of the best of each worlds.
This isn’t as straightforward because it sounds, nevertheless. To facilitate this team-up, the Parker Solar Probe would need to be inside the field of view of one among the Solar Orbiter’s instruments because the two observe the sun from their relative positions.
How scientists achieved the ‘better of each worlds’ to potentially solve a solar mystery
A team of astronomers, including Italian National Institute for Astrophysics (INAF) researcher Daniele Telloni, discovered that on June 1, 2022, the 2 solar observatories can be inside touching distance of the specified orbital configuration to have interaction in such a team-up.
Because the Solar Orbiter can be the sun, the Parker Solar Probe can be just off to the side, only a bit of bit out of view of the ESA spacecraft’s Metis instrument — a tool called a “coronagraph” that blocks out light from the photosphere to image the corona and is right for large-scale, distant observations.
To perfectly line up the 2 spacecraft and get the Parker Solar Probe in view of Metis, the Solar Orbiter performed a 45-degree roll and was then pointed barely away from the sun.
The information that was collected consequently of this well-planned maneuver authorized by the spacecraft’s operation team paid off, revealing turbulence that might indeed be transferring energy in the way in which solar physicists had theoretically predicted can be causing coronal heating.
The turbulence drives coronal heating in a way that is analogous to what happens when coffee is stirred here on Earth. Energy is transferred to smaller scales by random movements in a fluid or gas — coffee and plasma — and this converts that energy to heat. Within the case of the corona, plasma is magnetized, and which means stored magnetic energy can be converted to heat.
The transfer of magnetic and movement or kinetic energy from larger to smaller scales is the very essence of this turbulence, and on the smallest scales, it allows the fluctuations to interact with individual particles, mostly positively charged protons, heating them.
That isn’t to say the mystery of coronal heating is “case closed,” nevertheless. Solar scientists still need to substantiate the mechanism that has been hinted at by these results and by the collaboration between the Parker Solar Probe and the Solar Orbiter.
“It is a scientific first. This work represents a big step forward in solving the coronal heating problem,” Solar Orbiter Project Scientist Daniel Müller said.
The team’s research was published on Thursday (Sept. 14) within the Astrophysical Journal Letters.