Massive faint plasma loops were spotted above the Sun's surface after a strong solar flare. The loops linger like ghostly echoes from the solar storm.
Faint Loops of Plasma Spotted
On Monday (Jan. 29), a strong 6.8 magnitude M-class solar flare, the second-highest class of solar flares after X-class flares, erupted from sunspot AR3559 and started to fade below the Sun's western limb, according to Spaceweather.com.
Large loops of ionized gas, or plasma, frequently rise above the Sun's surface like enormous horseshoes before solar flares burst from the surface. The magnetic field lines of dark-colored sunspots hold these plasma loops, or prominences, in place. Eventually, solar flares cause these lines to snap like an elastic band, launching the looped plasma into space as a coronal mass ejection (CME).
A CME created by the latest star explosion was expected to pass quite close to Earth's magnetic field on Feb. 1. However, Spaceweather.com claims it missed us entirely.
But astrophotographer Eduardo Schaberger Poupeau captured an amazing image of faint plasma loops rising above the Sun's surface, precisely where the CME had burst from, soon after Monday's M-class flare. These loops are mysterious because, in theory, a CME containing all of the area's plasma should have been expelled into space.
NASA claims that the logic-defying structures, called post-flare loops (PFLs), only show up when the Sun is viewed through a filter that intensifies the red wavelengths of light emitted by hydrogen, or H-alpha.
A 2005 study found that PFLs are most frequently observed following M-class and X-class flares and often reach about 30,000 miles (50,000 kilometers) above the Sun's surface. The height of the most recent loops is unknown.
These bright arches on the Sun have previously been observed by astronomers, who have also observed them following explosions from other stars. Because the structures contain lesser amounts of plasma, which is much cooler and consequently gives off less light, they are much fainter than the prominences that occur before a solar flare. Few pictures of PFLs, therefore, depict the phenomenon in as much detail as Poupeau's most recent shot does.
What Are Post-Flare Loops
We frequently witness a sequence of loops above the Sun's surface in the hours after a solar flare called post-flare loops. The best way to see these loops is to look at the H-alpha emission or red-shifted light that hydrogen emits in the solar spectrum. The loops on the left were created during an active region's June 26, 1992 flare (AR 7205).
Time-lapse movies (1.3 MB MPEG movie or 3.5 MB Quicktime movie) demonstrate how material "condenses" into the tops of these loops from the Sun's heated corona and then flows down the loops' legs to the surface. The material can cool to far lower temperatures inside the magnetic limits of these loops, where it is partially isolated from the million-degree corona.
These specific loops are interesting because they contain a set of "bent-over" loops, which are important in some theoretical models of flares. The "Doppler effect," which shifts light traveling toward us toward the blue end of the spectrum and light traveling away from us toward the red end, can be used to calculate the velocity of the material flowing in these loops.
The three-dimensional flow of material within these loops can be determined using this information in conjunction with the observed motion of the material. They discovered that the loops create an arcade arranged in a row to resemble a tunnel.
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