The solar surface and squirted between the magnetic structures in the corona. View that coronal loops are hypervelocity currents of plasma blasted from These plasma blobs were moving at tremendous speeds, leading to the new However, movies made from observationsīy the TRACE (Transition Region and CoronalĮxplorer) spacecraft have shown bright blobs of plasma racing up and down Until recently, researchers had suspected that coronal loops were essentially In regions of the photosphere of opposite magnetic polarity to each other. The two ends of a loop, known as footprints, lie Larger faint ones, lastingĭays or weeks, are more typical of the quiet corona, when solar activity Spots, are common around the time of solar maximum. Ultraviolet, and white-light wavelengths, consisting of an arch, extending Other prominent ones are at 6375 Å and at 7892 Å.Ī coronal loop (Fig 2) is a feature in the Sun's corona visible at X-ray, The strongest of all is the greenĬoronal green line (due to the Fe 13+ ion) at 5303 Å. The Sun's corona caused by very high excitation Some exceptions have been observed by SOHO),Ĭoronal lines are strong emission lines in the spectrum of Wind and the exclusive source of its high-speed component.ĭuring the minimum years of the solar cycle,Ĭoronal holes are largely confined to the Sun's polar regions (although
Results in coronal holes being the primary source of the solar This open structure allows charged particles to escape from the Sun and Structure in other words, magnetic field lines emerging from the holesĮxtend indefinitely into space rather than looping back into the photosphere. Coronal holes are of very low density (typicallyġ00 times lower than the rest of the corona) and have an open magnetic field In pictures taken with a coronagraph or duringĪ total solar eclipse, and that shows up as a void in X-ray and extreme ultraviolet images. Coronal condensationsĪre seen at the Sun's limb above sunspot groups and show loop structures that outline magnetic field lines.Ī coronal hole is a region of the Sun's corona that appears dark To 4 million K) and denser than its surroundings. These give way to coronal holes at each pole and a sheet-like structure near the equator.Ī coronal condensation is an area of the Sun's corona that is hotter (up At solar maximum (the period of greatest activity during the solar cycle) theĭominant features are coronal loops and streamers associated with active regions, but at minimum Not only daily but over the course of a solarĬycle. The corona is extraordinarily dynamic with an appearance that changes, Movies made from X-ray pictures show that Is caused by sunlight scattering or reflecting off dust in interplanetary The F corona (Fraunhofer corona), lying outermost, The K corona (or continuum corona), which is the innermost part of the corona closestĪbout two solar radii, is caused by sunlight scattering off electrons. The faint E corona (emissionĬalcium, iron, and some other elements. The so-called white-light corona, visibleĭuring a total eclipse (Fig 1) or with a coronograph, It consists of hot (one to four million K), low-density (about 10 -16 g/cm 3) gas that extends for millions of kilometers from the (or another star's) atmosphere lying immediately above the chromosphere, In solar physics, the corona is the tenuous uppermost level of the Sun's
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