2,674 research outputs found
Eruptions from solar ephemeral regions as an extension of the size distribution of coronal mass ejections
Observations of the quiet solar corona in the 171A (~1MK) passband of the
Transition Region and Coronal Explorer (TRACE) often show disruptions of the
coronal part of small-scale ephemeral bipolar regions that resemble the
phenomena associated with coronal mass ejections on much larger scales:
ephemeral regions exhibit flare-like brightenings, rapidly rising filaments
carrying absorbing material at chromospheric temperatures, or the temporary
dimming of the surrounding corona. I analyze all available TRACE observing
sequences between 1998/04/01 and 2009/09/30 with full-resolution 171A image
sequences spanning a day or more within 500 arcsec of disk center, observing
essentially quiet Sun with good exposures and relatively low background. Ten
such data sets are identified between 2000 and 2008, spanning 570h of observing
with a total of 17133 exposures. Eighty small-scale coronal eruptions are
identified. Their size distribution forms a smooth extension of the
distribution of angular widths of coronal mass ejections, suggesting that the
eruption frequency for bipolar magnetic regions is essentially scale free over
at least two orders of magnitude, from eruptions near the arcsecond resolution
limit of TRACE to the largest coronal mass ejections observed in the inner
heliosphere. This scale range may be associated with the properties of the
nested set of ranges of connectivity in the magnetic field, in which
increasingly large and energetic events can reach higher and higher into the
corona until the heliosphere is reached
Active region evolution in the chromosphere and transtition region
Images in the C IV 1548 A and the Si II 1526 S lines taken with the ultraviolet spectrometer polarimeter (UVSP) instrument on board the Solar Maximum Mission (SMM) satellite were combined into movies showing the evolution of active regions and the neighboring supergranulation over several days. The data sets generally consist of 240 by 240 arc second rasters with 3 arc second pixels taken one per orbit (about every 90 minutes). The images are projected on a latitude/longitude grid to remove the forshortening as the region rotates across the solar disk and further processed to remove jitter and gain variations. Movies were made with and without differential rotation. Although there are occasional missing orbits, these series do not suffer from the long nighttime gaps that occur in observations taken at a single groundbased observatory and are excellent for studying changes on time scales of several hours. The longest sequence processed to date runs from 20 Oct. 1980 to 25 Oct. 1980. This was taken during an SMM flare buildup study on AR 2744. Several shorter sequences taken in 1980 and 1984 will also be shown. The results will be presented on a video disk which can be interactively controlled to view the movies
Monomer reactivity in free-radical copolymerization : high-pressure copolymerization as a tool in revealing structure-reactivity relations
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