This movie is built from images taken over 10 days during the full perihelion encounter when the spacecraft was nearing the Sun’s corona. The perihelion is a brief moment during the encounter time, when the spacecraft is at its closest point to the Sun. The movie is from orbit 10 and dates and distances are on the frames, and changing locations of planets are in red.  (AHL/JHU; NASA)

To borrow from singer Paul Simon, these are definitely days of miracles and wonders — at least when it comes to exploring and understanding our Sun.

The Parker Solar Probe has been swinging further and further into the Sun’s corona, having just finished its 12th of 24 descents into a world of super-heated matter (plasma) where no human creation has ever gone.

The probe has dipped as close as 5.3 million miles from the surface of the sun — Mercury is 32 million miles from that solar surface — and is flying through the solar wind, through streamers (rays of magnetized solar material)  and even at times through coronal mass ejections, those huge eruptions of magnetized plasma flying at speeds up to nearly 2,000 miles per second.

This is all a goldmine for solar scientists, an opportunity to study our star — and by extension all stars — up close and to learn much more about how it works.

At a four-day conference at the Johns Hopkins University Applied Physics Lab late last month, scores of scientists described the results of their early observations and analyses of the measurements and images coming from the Parker Probe via its The Wide-Field Imager (WISPR) and instruments that measure energy and magnetic flows.  The results have often surprising and, as some scientists said, “thrilling.”

“Parker Solar Probe was developed to answer some of the biggest puzzles, biggest questions about our Sun,” said Nour Raouafi, project scientist for the Parker Solar Probe.

“We have learned so much that we believe we are getting close to finding some important answers.  And we think the answers will be quite big for our field, and for science.”

The Parker Solar Probe had observed many switchbacks in the corona— traveling disturbances in the solar wind that cause the magnetic field to bend back on itself.  They are an as-yet unexplained phenomenon that might help scientists uncover more information about how the solar wind is accelerated from the Sun. (NASA’s Goddard Space Flight Center/Conceptual Image Lab/Adriana Manrique Gutierrez)

Among the many unexpected solar features and forces detected by the Parker Probe is the widespread presence of switchbacks, rapid flips of the Sun’s magnetic field moving away from the Sun.  Some of these were seen from afar by earlier solar missions, but the Parker Probe has found them to be common as the spacecraft gets further into the corona and quite possibly closer to understanding several of its key science goals.

A primary goal  of the Parker mission is to identify the origins of the solar wind,  the supersonic blasts of plasma and other particles which fly constantly off the Sun and constitutes the “space weather” that permeates and protects our solar system and beyond.   Another key goal is to solve the puzzle of why the corona, or solar atmosphere, is substantially hotter than the solar surface.

Nour Raouafi, project scientist for the Parker Solar Probe, alongside the spacecraft before launch. (NASA)

These are fundamental issues regarding the Sun that were explored in theory decades ago by pioneering solar and astrophysicist Eugene Parker, for whom the probe is named, and others.  But while the existence of the solar wind and the extreme heat of the corona have been long since confirmed, the stellar forces at work behind those theories have remained beyond the capacity of science to confirm or disconfirm.

Marco Velli of the University of California, Los Angeles — who was Observatory Scientist for Parker Solar Probe until launch and now one of the leading mission scientist — described major progress on three fronts early in the conference.

First, he said, the Parker Probe is picking up the presence of far more beams of highly-energetic particle than expected — a finding with major implications for the origins of the solar wind.  These particles are the product of continuous magnetic breakings and re-connections on the Sun’s surface and appear to play a role in accelerating the solar winds to the range of 300  (the slow wind) to 600 miles per second (the fast wind.) Velli said these particles are similar to cosmic rays.

Then he described the presence of many “humongous” magnetized alpha waves of particles coming off the Sun — another key finding for understanding how the solar wind travels and perhaps why the corona is so hot.  Velli likened these switchbacks to “huge surfer waves that bend over backwards” and contribute to pushing the wind outward.

Marco Velli is Professor of Space Physics at  University of California, Los Angeles. (UCLA)

And then there was the finding that the relationship between closed and open magnetic fields is dynamic on the Sun.

He said that scientists used to think the two magnetic polarities of the Sun were separated by what was by  a smooth curtain-like structure. “But Parker, via WISPR and other measurements, makes clear that the sheet is not stable but continuously being broken up and blown apart by plasma blobs,” which are emitted outward from tips of magnetic fields.

When you step back and to consider what the Parker Probe is actually doing, it is identifying, measuring, categorizing and sometimes imaging the workings of the surface and corona of a star, and is doing this from remarkably close. It’s an all-time first.

Over years, these results will allow scientists to make much better sense of how our Sun actually sends life-giving (as well as hazardous) solar material our way.

The Sun and its corona are extremely dynamic, a reality that until recently was only apparent during solar eclipses. This large field-of-view image taken by the European Space Agency’s PRoject for Onboard Autonomy 2 (PROBA2) spacecraft provides an opportunity to study extended coronal structures observed in the extreme ultraviolet in conjunction with global coronal magnetic field simulations. The Parker Solar Probe is descending into the region near where coronal structures speed outward. (ESA)

To return to the opening image,  here is what you are seeing:

The Probe is looking at the Sun from an angle, and the telescope image on the right starts with fuzzy white dots.  Those are stars.

The white streaks that cross the screens are dust particles hitting the telescope lenses.  Although the solar wind fills many parts of the corona with plasma and particles, they are not picked up visually unless there are other features such as magnetic field lines.

The blobs that come into the images at about 20 seconds are the coronal mass ejections (CMEs,) and at 30 seconds there is an apparent collision between two CMEs at the lower left.  At the upper left at 20-25 seconds is what appears like a flowing mass that is, most likely, the slow solar wind with “streamer” features that amplify it visually.  Here are more streamers below.

The video covers a period of about 10 days.

These images show coronal streamers on the Sun, bright structures in the corona normally seen only in solar eclipses, as imaged by NASA’s Parker Solar Probe. Coronal streamers are structures of solar material and magnetic field within the Sun’s atmosphere, the corona. They usually overlie regions of increased solar activity. (NASA/Johns Hopkins APL/Naval Research Laboratory)

Unlike Earth, the Sun doesn’t have a solid surface. But it does have a superheated atmosphere, made of solar material bound to the Sun by gravity and magnetic forces. As rising heat and pressure push that material away from the Sun, it reaches a point where gravity and magnetic fields are too weak to contain it.

That point, known as the Alfvén critical surface, marks the end of the solar atmosphere and beginning of the solar wind.  Solar material with the energy to make it across that boundary becomes the solar wind, which drags the magnetic field of the Sun with it as it races across the solar system, to Earth and beyond. Importantly, beyond the Alfvén critical surface (named after Swedish solar physicist Hannes Alfvén)  the solar wind moves so fast that waves within the wind cannot ever travel fast enough to make it back to the Sun – severing their connection.

The slow solar wind (traveling at some 300 miles per second) is associated with streamers and comes off the Sun’s equatorial region.  The fast solar wind (as much as 600 miles per second) is known to originate at the poles.

Until now, researchers were unsure exactly where the borders of the Alfvén critical surface lay. Based on remote images of the corona, estimates had put it somewhere between 10 to 20 solar radii from the surface of the Sun – 4.3 to 8.6 million miles.

On April 28, 2021, during its eighth flyby of the Sun, Parker Solar Probe encountered specific magnetic and particle conditions at 18.8 solar radii (around 8.1 million miles) above the solar surface that told scientists it had crossed the Alfvén critical surface for the first time and entered the solar atmosphere.

This is a small part of the solar atmosphere, with an unexpected multitude of small loops, bright spots and dark, moving fibrils in the white rimmed squares. The tiny brightening dots and loops sparked immediate excitement as they show up remarkably sharp and contrasted, ubiquitously all over the so-called “quiet Sun” where nothing seemed to happen. But now, looking at this high resolution, we see very tiny light flashes almost everywhere. These light flashes recently called ” campfires” may well be the “nanoflares” theorized by Gene Parker decades ago.  ( ESA/Solar Orbiter/EUI Team: CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL.

The long debate over the origins of the supersonic solar wind — and of the super-hot corona — has tended to be between those who see Alfvén waves or “nanoflares” as the primary instigator.

Alfvén waves were first proposed in the 1940s and are made up of plasma, the fourth state of matter. Plasma is created where gas is so hot that atoms are stripped of their electrons, and it is by far the most common state of matter in the universe.  Plasma makes up most of the Sun and other stars.

Because plasma is electrically charged, it couples with electrical and magnetic fields, which leads to the creation of many kinds of powerful waves.  Some scientists have argued that Alfvén waves rise from below the Sun’s corona and push the solar wind to its supersonic speeds and heat the the corona as well.

But scientists led by Gene Parker have had a different view.  Since the 1970s, Parker theorized that “nanoflares” on the surface of the Sun were a primary source of extreme coronal heating and some aspects of the solar wind. These relatively small bursts result in the breaking and re-connecting of magnetic fields and are theorized to produce the heat and energy need for the supersonic solar wind and the hot corona.

This has been quite a debate in the world of heliophysics, but it has remained unresolved because of the absence of necessary data.

However, Parker Probe Project Scientist Raouafi said the necessary data is coming in and it may be that both nanoflares and Alfvén waves are integral parts of both the solar wind and the hot corona.

David J. McComas of the Princeton Plasma Physics Laboratory also sees a theoretical converging regarding the key mission issues, based on the data from the Parker Probe.

“Yes, we are getting closer to an answer on those questions, sorting out which theories are right and which are not,” he said.  “After those are resolved, I’m sure, we’ll just get to the next layer of the onion.  Sun science is messy….But understanding the source of energy in our solar system is a profound thing to do.”

The Parker Probe nominal mission has three more years to go and 12 more passes into the corona, each a little further in.  And the 11-year solar cycle will get significantly stronger as the mission continues and solar characteristics and behaviors will become increasingly active apparent.

Hold on to your seat.