Solar Dermatology - A brief tour through the esoteric terminology

1. Solar Dermatology - A brief tour through the esoteric terminology Anemone Arcade Bright Point Coronal Hole Coronal Mass Ejection Coronal Rain Cusp Disparation Brusque Erupting Filament Eruptive Prominence Evershed Flow Faculae Filamant Filigree Moreton Wave Moss Nanoflare Network Neutral Line Plage Polar Plume Pore Postflare Loops Prominence Streamer Belt Spicule Sunspot Penumbra Sunspot Umbra Supergranulation Two-Ribbon Flare Tadpole

2. The blemished sun! Ourselves, the dermatologists. In 1611, Galileo wrote: "Spots are on the surface of the solar body where they are produced and also dissolved, some in shorter and others in longer periods. They are carried around the Sun; an important occurrence in itself." Galileo's drawings from 2 June 8 July 1613 are shown as a movie above. Galileo’s ideas got him into trouble with church leaders, because all heavenly bodies were supposed to be perfect, that is “without blemish”.

3. Coronal Hole: A region of the Sun’s corona that appears dark in pictures taken with a coronagraph, and that shows up as a void in X-ray and extreme ultraviolet images. Coronal holes are of very low density (typically 100 times lower than the rest of the corona) and have an open magnetic field structure. This open structure allows charged particles to escape from the Sun and results in coronal holes being the primary source of the solar wind.

4. Anemone (Windflower): An active region that, when viewed in the corona, does not have connections to any other magnetic concentrations. This often happens when an active region emerges in a coronal hole. Arcade: A system of loops observed in the solar atmosphere, thought to be structured by magnetic fields and brightened after a flare. Trace 171 Angstrom image,~1 x 106 K 8 Nov 2000. (Loops are on the order of 100 Mm above the loop footpoints.)

5. Q: What are some of the most outstanding questions in Solar Physics? A: Spiro Antiochos: “Why do the loops in the corona look so smooth if they are supposed to be tangled and mangled by the photospheric motions? There is thought to be a tangling that produces complex geometries that, in turn, lead to nanoflares releasing energy through magnetic reconnection. However, in the TRACE images, the loops look smooth and parallel, i.e., combed.”

6. Coronal Rain: Material that condenses in the Sun’s corona and falls along curved paths onto the chromosphere. Observed in H-alpha light at the solar limb above strong sunspots, coronal rain consists of gas ejected by a loop prominence that returns, several hours later, along the outline of the now invisible loop. Coronal Mass Ejection: A huge eruption of material from the Sun’s corona into interplanetary space. CMEs are the most energetic of solar explosions and eject up to100 billion kilograms of multi-million-degree plasma at speeds ranging from 10 to 2,000 km/s. They often look like bubbles. CMEs originate in regions where the magnetic field is closed. These storms can disrupt power grids, damage satellite systems, and threaten the safety of astronauts. (X17 and X10 flares and the two associated CME’s, LASCO C2)

7. Filament: A strand of relatively cool gas suspended by magnetic fields over the solar photosphere so that it appears as a dark line over the Sun’s disk. A filament on the limb of the Sun seen in emission against the dark sky is called a prominence. Filaments often mark areas of magnetic shearing and can be seen only in the centers of strong spectral line, such as H-alpha or the H and K lines of calcium.

8. Filament: This brief movie shows 3 frames. The first shows the Sun in white light taken by the MDI instrument. This instrument observes the Sun's surface and does not "see" the filaments at all. However, this image is then replaced by an EIT 195 instrument image in which the subtly darker filaments can be discerned. Finally, an EIT 304 image is revealed underneath in which the filaments are even easier to see.

9. Erupting Filament: The disappearance of a filament, often associated with a flare. The filament erupts into the corona. There is an activation phase with increased mass motions, expansion, etc. When these eruptions are observed on the limb - they are known as erupting prominences. Disparation Brusque: The sudden disappearance of a filament. A filament in Jan 2007 shown in O V line and a day later caught as it is erupting.

10. Sunspot Umbra: the dark core of a sunspot, cooler than the surrounding photosphere because is suppresses convection. Average size is ~10000 km, but can be as large as 60000 km. Sunspot Penumbra: the lighter areas, marked by a radial filamentary structure. Typical size is ~5000 km. Waves are observed to move across the penumbral structures. Structure is thought to be ‘uncombed’. Image credit: Friedrich Woeger, KIS, and Chris Berst and Mark Komsa - taken here at the Dunn Tower.

11. Evershed Flow: The horizontal flow of gas in the penumbrae of a sunspots; the effect is named after its discoverer, the English astronomer John Evershed (1864-1956). The maximum outflow velocity is about 2 km/s. Image from Tom Berger, Dutch Open Telescope.

12. Q: What are some of the most outstanding questions in Solar Physics? A: Gene Parker: “The Sunspot is without explanation. Why is the Sun obliged to create them? We understand a lot about them, excepting why the Sun is compelled by the basic laws of physics to create cool, magnetic spots.” .  Other main sequence stars show evidence of ‘starspots’ and cyclical magnetic activity.  Other stars show evidence of an atmospheric temperature inversion which means that coronal heating and corona formation is a universal process for cool stars.

13. Granulation: caused by convection, the grainy appearance of the solar photosphere is produced by the tops of these convective cells.The rising part of the granules is located in the center where the plasma is hotter. The outer edge of the granules is darker due to the cooler descending plasma. The diameter of a typical granule is on the order of 1000km and lasts 8 to 20 minutes before dissipating. The vertical flow is ~ 1 km/s. Hinode movie in G-band (430 nm) and Ca II H (397 nm) showing granules and flux. Bright Point: bright regions observed in intergranular lanes. They are thought to be magnetic flux tubes and are bright due to hot-wall radiation. Often observed in ‘G-band’ - 430.5 nm.

14. Filigree: A string of bright points on the Sun's photosphere that are sometimes visible in intergranular lanes in continuum images; the smallest points are only about 150 km and last for hours. Filigrees are thought to be places where flux tubes penetrate the photosphere. Filigree were originally observed in H-alpha, but are also seen in G-band.

15. Plage: observed as bright features in chromospheric emission and are found surrounding sunspots (active regions). Plage are linked to the increased irradiance during solar maximum.

16. Faculae: A bright area observed near the limb, commonly seen near an active region, such as a sunspot, or where such a region is about to form. Faculae, which last on average about 15 days. Faculae are the chromospheric signature of filigree. In high-res, the facular grains appear as brightenings projected on the limbward neighboring granule - the ‘hot wall’ effect. www.uni-sw.gwdg.de/.../ solphys/egranulen.html

17. Moreton Wave: A shock wave in the Sun’s chromosphere that is produced by a large solar flare and expands outward at about 1,000 km/s. It usually appears as a slowly moving diffuse arc of brightening in H-alpha or coronal line, and may travel for several hundred thousand km. Moreton waves are always accompanied by meter-wave radio bursts; they are named after the American solar astronomer Gail Moreton. Nanoflare: A proposed coronal heating mechanism in which small-scale currents are dissipated through impulsive magnetic reconnection (Parker, 1988). Each event releases ~ 1024 ergs and has an associated plasma flow that broadens coronal lines.

18. Moss:TRACE May 30, 1998. In this image, there is a blue, black and white spongy structure between the bases of the coronal loops. Solar moss consists of hot gas which emits extreme ultraviolet light. It occurs in large patches, about 15,000 km in extent, and appears between 18,000 km above the Sun's visible surface. It looks "spongy" because the patches are composed of small bright elements interlaced with dark voids caused by jets of cooler gas from the chromosphere. The solar moss appears only below high pressure coronal loops in active regions, typically persisting for a day.

19. Supergranulation: interpreted as the largest scale of convection, roughly 30,000 km cell size. It is a predominantly horizontal flow with velocities of 300-500 m/s observed in the photosphere. In comparison, the vertical upflow at the cell center is on the order of 50 m/s and downflow at the cell boundaries is 100 m/s. “Orange peel” image: doppler velocity with rotation subtracted and p-modes removed. (Hathaway, MDI) Network: Chromospheric emission spatially correlated with the supergranulation cell boundaries. It is believed that the horizontal flow of supergranulation sweeps magnetic fields into the cell boundaries. Lifetime of the network is ~ 1 day. Best seen in Ca II H & K.

20. Polar Plumes: Polar plumes appear prominently in white light coronagraph observations of coronal holes as distinct, strongly collimated flow tubes. They might carry the bulk of the mass and energy of the solar wind emanating from polar regions. Electron density is greater in plumes (8x). Temperature is lower (20%). Density contrast between plume and inter-plume area disappears by 7 Rsun. The image (Dec 23 1996) shows the Streamer Belt along the Sun's equator, where the low latitude solar wind originates. Over the polar regions, one sees the polar plumes all the way out to the edge of the field of view. The frame was selected to show Comet SOHO-6, one of seven sungrazers discovered by LASCO, before it plunged into the Sun.

21. Pore: the smallest magnetic phenomena on the Sun which can be distinguished in white light. They have no penumbra and are much smaller than sunspots - the size of one or a few granules. Lifetimes are on the order of a day. Magnetic field is ~ 1500 Gauss.

22. Q: What are some of the most outstanding questions in Solar Physics? A: Han Uitenbroek: “How does the magnetic flux stay coherent as it rises through the convection zone to the solar surface? The forces it experiences en route should shred it -- only a strong twist could keep it together. Do we observe this twist?” . Yuhong Fan’s 1999 simulation of a flux tube rising and experiencing a kink instability.

23. Q: What are some of the most outstanding questions in Solar Physics? A: Aimee Norton: “How strongly coupled are the North and South hemispheres of the Sun? The sunspot cycle and the polar field strengths have been seen to progress at least 6-10 months out of phase in the last cycle. How out of phase can the hemispheres get? ” .

24. Two ribbon flare: Two ribbons lie at the feet of the flare loops, often occurs in a decaying active region. Neutral line runs parallel to and in between the ribbons - 195 Angstroms Trace. The backbone is the Cusp , it would be the apex of the loops if viewed edge-on. NEXT MOVIE: Post-flare loops: Transverse structures located between the two ribbons after a flare, seen in H-alpha, transition zone and coronal lines. Arcade & Tadpoles also seen in the next movie. Trace 171 Angstroms.

25. Q: What are some of the most outstanding questions in Solar Physics? A: Joe Giacalone: “The Sun is an efficient particle accelerator. How? You’ve heard one theory - perpendicular shocks - but it remains an open-ended question.” Image from ACE. .

27. Prominence: an elongated structure full of material 100x cooler and denser than the corona (like cool clouds). Held up by magnetic structures, they can live for weeks/months, and are seen as bright against the black background of space. They can reach heights of several 100,000 km above the limb. They eventually become unstable and erupt. A prominence would be a filament if observed on the disk. Hedgerow: A series of filament/prominence loops that appear like croquet loops and have adjacent ‘legs’.

28. Prominence, spicule forest, Hinode SOT wing of H-alpha Q: A: Rob Rutten “Why do you see all the mottles, fibrils, spicules, etc, in H-alpha and not Ca II K? Ca II K is supposed to be more opaque than H-alpha.”

29. Spicules: jets of hot material seen in the chromosphere, flowing 20 km/sec from the photosphere, lasting about 5 minutes, structured by the magnetic field. Thought to be caused by acoustic waves leaking through the atmosphere. Swedish Solar Telescope. Spicules are also referred to as fibrils and mottles.

30. More Outstanding Questions in Solar Physics: Spiro Antiochos: What is the structure of the magnetic field in a filament/prominence? Is it loops? Is it twisted spaghetti? Structure. Where does the ejection first start - high or low? Rob Rutten: Why do I see the same active region pattern in H-alpha and TRACE 195? H-alpha is 10000 K (low chromosphere) and Trace 195 1.5 x 10^6 K (corona). Shouldn’t they look different? Aimee Norton How can the toroidal field at the base of the convection zone be super-equipartition? 30-100 kiloGauss? Gene Parker: When you write down the dynamo equations - one is the strength of cyclonic convection and the other is nonuniform rotation, need to put in effective turbulent diffusion coefficient (10^11 cm^2/s). Only turbulent diffusion can fit this bill. So we look at the surface and we see turbulence and convection - 300 km scale, velocity 1 km/s. Turbulent should be 1/3 * scale *vel = 10^11. What is the problem? Turb. Diffusion is based on scalar quantity but we need a vector field which has its own internal stresses. Lower conv. Zone - 2-3000 G stored through. And this force is equal to the turb diffusion. How does turb difficusion proceed? (same problem exists with the galaxy - need 10^25 cm^2/s . How does turb diffusion work with the current dynamo. Internal rotation profile of the sun is not reproduced by hydrodynamics. So we infer magnetic field stresses are involved.

31. More Outstanding Questions in Solar Physics: Spiro Antiochos: What is the structure of the magnetic field in a filament/prominence? Is it loops? Is it twisted spaghetti? Structure. Where does the ejection first start - high or low? Rob Rutten: Why do I see the same active region pattern in H-alpha and TRACE 195? H-alpha is 10000 K (low chromosphere) and Trace 195 1.5 x 10^6 K (corona). Shouldn’t they look different? Aimee Norton: How can the toroidal field at the base of the convection zone be super-equipartition? 10^5Gauss! Emerging flux tube models have inferred a strong super-equipartition field strength of order 10-100 times the kinetic energy density of the differential rotation. How is this? (Parker, 1994) Gene Parker: When you write down the dynamo equations - one important ingredient is the strength of cyclonic convection and the other is nonuniform rotation. However, you need to include an effective turbulent diffusion coefficient (10^11 cm^2/s). Only turbulent diffusion can fit this bill. How can we include an effective turbulent diffusion term that works withour current picture of the solar dynamo? This same problem exists with the galactic dynamo!

32. GEEK PICTIONARY! The Rules: Come up and draw a solar and heliospheric ‘phrase’. You will compete against another team that is drawing the same term. No symbols, numbers, or words can be drawn on your page.

33. More Outstanding Questions in Solar Physics: Spiro Antiochos: What is the structure of the magnetic field in a filament/prominence? Is it loops? Is it twisted spaghetti? Structure. Where does the ejection first start - high or low? Rob Rutten: Why do I see the same active region pattern in H-alpha and TRACE 195? H-alpha is 10000 K (low chromosphere) and Trace 195 1.5 x 10^6 K (corona). Shouldn’t they look different? Aimee Norton How can the toroidal field at the base of the convection zone be super-equipartition? 10^5Gauss! Thin flux tube models of emerging flux loops through the solar convective envelope (Sectionﾊ5.1) have inferred a strong super-equipartition field strength of order for the toroidal magnetic field at the base of the solar convection zone. Generation of such a strong field is dynamically difficult since the magnetic energy density of a field is about 10-100 times the kinetic energy density of the differential rotation, Parker, 1994, Rempel and Schussler, 2001. Gene Parker: When you write down the dynamo equations - one important ingredient is the strength of cyclonic convection and the other is nonuniform rotation. However, you need to include an effective turbulent diffusion coefficient (10^11 cm^2/s). Only turbulent diffusion can fit this bill. So we look at the surface and we see turbulence and convection - 300 km scale, velocity 1 km/s. Turbulent should be 1/3 * scale *vel = 10^11. What is the problem? Turb. Diffusion is based on scalar quantity but we need a vector field which has its own internal stresses. Lower conv. Zone - 2-3000 G stored through. And this force is equal to the turb diffusion. How does turb difficusion proceed? (same problem exists with the galaxy - need 10^25 cm^2/s . How can we include an effective turbulent diffusion term that works withour current picture of the solar dynamo? Internal rotation profile of the sun is not reproduced by hydrodynamics. So we infer magnetic field stresses are involved.