The Solar Dynamics Observatory caught a splendid example of broadening coronal loops seen in profile at the edge of the Sun. Credit: NASA/Solar Dynamics Observatory
Weve all seen the beautiful images and videos of coronal loops. Theyre curved magnetic kinds that force vibrantly radiant plasma to take a trip along their path. They arch up above the Sun, in some cases for countless kilometers, prior to reconnecting with the Sun again.
However a new research study states that some of what were seeing arent loops at all. Rather, theyre a kind of optical impression. Do we understand the Sun as well as we think we do?
The Suns corona is the outer layer of its environment. Its made of plasma, which consists of great deals of charged particles. That implies that it readily reacts to electromagnetic fields. The Sun has a powerful electromagnetic field that differs by place and time. Sometimes that magnetism drives the plasma high above the corona, forming fantastical structures called coronal loops that ultimately reconnect to the Suns surface area. A few of these structures can last for days and even for weeks.
” This is a totally new paradigm of comprehending the Suns environment.”– Anna Malanushenko, lead author.
If this brand-new research study is appropriate, then it means that numerous of what appear to be loops arent loops.
The brand-new research study is released in The Astrophysical Journal. Its title is “The Coronal Veil.” Anna Malanushenko, a researcher at the National Center for Atmospheric Research, is the lead author.
The research study is based on an advanced 3D simulation of the Suns corona. It permitted researchers to separate individual coronal loops by slicing the corona into unique areas. The researchers discovered some loops, however their outcomes revealed that much of what looked like loops werent loops at all.
” I have actually spent my entire profession studying coronal loops,” said lead author Malanushenko. “I was excited that this simulation would give me the chance to study them in more information. I never anticipated this. My mind exploded when I saw the results. This is a totally new paradigm of understanding the Suns atmosphere.”
Coronal loops radiance brilliantly in extreme UV radiation due to their temperature. The new research study does not completely refute the presence of loops.
This new research makes researchers rethink at the Sun and its habits. The authors of this paper are puzzled because the coronal loops dont seem to conform to what they understand about magnetism.
If coronal loops are certainly loops that stream along the Suns field lines, they ought to spread out apart the even more they get from the Sun. … coronal loops appear to do not have anticipated visual growth with height, as the restricting magnetic field damages with elevation on average in the corona,” the authors point out in their paper.
If theyre not loops, what are they?
According to the research study, some of them are illusions that theyre calling the “coronal veil.” And their presence is making the authors question what they thought they learnt about the Sun.
Coronal loops, observed in the ultraviolet radiation Fe IX 17.1 nm (171 Å) by the TRACE spacecraft on November 6, 1999, extending 120,000 km off the Suns surface area. Credit: NASA/TRACE
” This study reminds us as researchers that we should constantly question our assumptions which often our instinct can work versus us,” Malanushenko stated.
A few of the loops are what theyre calling forecast artifacts. However its difficult to discern between the actual coronal loops and artifacts. “We demonstrate the problem of discerning from observations whether a specific loop corresponds to a strand in the volume or a projection artifact. We show how apparently separated loops might deceive observers, even when observations from multiple seeing angles are available,” the authors write.
The simulation is called MURaM. MURaM is a practical simulation that extends from deep inside the Sun– about 10,000 km listed below the surface– up to almost 40,000 km into the corona.
MURaM permitted researchers to observe the complete life process of a solar flare, starting from deep within the Sun, to the flares emergence on the surface, to its explosive release into space.
But the main result as far as this study is concerned is the data set produced by MURaM. These data sets include the magnetic fields structure and the plasma that complies with it. MURaM permits researchers to develop observations of the Sun, consisting of the corona, that are “synthetic.” The Suns corona is optically thin, which suggests that its easy to translucent. While that might sound like an observational benefit, thats not always the case.
When we observe the Sun, that optical thinness means that structures like coronal loops can overlap one another. And its challenging to tell which may be in the foreground and which are in the background. The optical thinness likewise makes it tough to recognize how thick the loops are. Are they thick, sort of like a garden pipe? Or are they thin, like a ribbon seen on its edge?
Theres a third possibility when seeing these loops in the optically thin corona. Instead of a thin strand, loops might be a visual fallacy triggered by a fold in a sheet of plasma.
MURaM is among the most powerful solar simulations ever produced. Its tested robust in many ways, however scientists are still careful. In this paper, the group compared their MURaM information with real pictures of the Sun from the Atmospheric Imaging Assembly (AIA) instrument on NASAs Solar Dynamics Observatory (SDO.).
Images a to d, and f, are AIA images that highlight a specific part of a coronal loop. E is an image from the MURaM simulation. Credit: Malanushenko et al. 2022.
The MURaM simulations strength is that scientists can dissect the data from the simulation in a way thats not possible with actual observations. MURaM produces information cubes that allow researchers to study areas of the Sun in a method that present observatories and instruments cant.
” Because loops comply with field lines, researchers presume that the loops are plane-of-sky projections of thin magnetic flux tubes full of plasma of different temperatures and densities,” the authors write in their paper. “The locations in between these flux tubes are also filled with magnetic fields, but the plasma is fainter since its less dense. Or it could be a different temperature level that does not appear well in the wavelengths of the instrument noticing it.”.
The authors studied volumetric emission to see these fainter locations in between the flux tubes. Thin slices of MURaM enabled the scientists to dissect the information and search for structures and behavior that arent evident in genuine images. These pieces show that some of what appear to be coronal loops arent loops however are made of ridges and wrinkles in the plasma.
These images from the research study show whats called volumetric emission. Theyre thin slices of images from MURaM data cubes. The majority of these images consist of massive structures of complex shape, with many ridges and wrinkles, instead of structures representing specific coronal loops. These structures are difficult to separate from one another. While some loops could be mapped to unique, brilliant blobs, numerous loops do not appear to refer the isolated structures in the volume. Image Credit: Malanushenko et al. 2022.
This research study raises questions about our understanding of the Sun. One of the drawbacks of the research study is that its based on a simulation. The authors acknowledge this, and that simulations play a more popular and more considerable function in astronomy and astrophysics as time goes on.
Can we trust MURaM?
The authors explain that MURaM is one of the most realistic simulations to date. Since it produces many things we can clearly observe about the Sun, we know this. “However, it is definitely vulnerable to criticism, like any other simulation. We however think that our results are relevant to the actual corona …” they mention.
Whats compelling about this discovery is that MURaM isnt the only simulation to produce outcomes supporting this studys conclusion.
A research study from 2005 based upon a different simulation found that the footprint of some coronal loops “… are wrinkled and not geometrically easy …” The authors of this new research say that supports their conclusion that some coronal loops are, in fact, not loops.
Another study in 2014 based on coronal simulations also found emissions that dont look like loops. Images from that simulation showed a scattered element, a number of separated blobs, and thin, intense, sheet-like structures similar to what MURaM revealed in this new research. Wrinkles in those sheet-like structures produced loops that looked like the forecast artifacts discovered in this new research study.
This figure is from a 2014 paper based upon different coronal simulations. It reveals (a) a diffuse part, (b) a number of separated blobs, and (c) thin, brilliant, sheet-like structures. Credit: Winebarger et al. 2014.
The next logical question to ask is: how numerous of the coronal loops are real loops, and how lots of arent? Itll also need new data handling techniques.
” We know that designing such methods would be incredibly challenging, but this study shows that the method we presently translate the observations of the Sun might not be appropriate for us to really comprehend the physics of our star,” Malanushenko said.
Initially released on Universe Today.
Referral: “The Coronal Veil” by A. Malanushenko, M. C. M. Cheung, C. E. DeForest, J. A. Klimchuk and M. Rempel, 2 March 2022, The Astrophysical Journal.DOI: 10.3847/ 1538-4357/ ac3df9.
The scientists discovered some loops, however their outcomes showed that many of what looked like loops werent loops at all.
If coronal loops are indeed loops that flow along the Suns field lines, they should spread out apart the even more they get from the Sun.” Because loops conform to field lines, researchers assume that the loops are plane-of-sky forecasts of thin magnetic flux tubes full of plasma of various temperature levels and densities,” the authors compose in their paper. These pieces show that some of what appear to be coronal loops arent loops however are made of ridges and wrinkles in the plasma.
The next rational concern to ask is: how numerous of the coronal loops are actual loops, and how numerous arent?