42 research outputs found
Investigation of solar active regions at high resolution by balloon flights of the solar optical universal polarimeter, definition phase
The definition phase of a scientific study of active regions on the sun by balloon flight of a former Spacelab instrument, the Solar Optical Universal Polarimeter (SOUP) is described. SOUP is an optical telescope with image stabilization, tunable filter and various cameras. After the flight phase of the program was cancelled due to budgetary problems, scientific and engineering studies relevant to future balloon experiments of this type were completed. High resolution observations of the sun were obtained using SOUP components at the Swedish Solar Observatory in the Canary Islands. These were analyzed and published in studies of solar magnetic fields and active regions. In addition, testing of low-voltage piezoelectric transducers was performed, which showed they were appropriate for use in image stabilization on a balloon
A solar magnetic and velocity field measurement system for Spacelab 2: The Solar Optical Universal Polarimeter (SOUP)
The Solar Optical Universal Polarimeter (SOUP) flew on the shuttle mission Spacelab 2 (STS-51F) in August, 1985, and collected historic solar observations. SOUP is the only solar telescope on either a spacecraft or balloon which has delivered long sequences of diffraction-limited images. These movies led to several discoveries about the solar atmosphere which were published in the scientific journals. After Spacelab 2, reflights were planned on the shuttle Sunlab mission, which was cancelled after the Challenger disaster, and on a balloon flights, which were also cancelled for funding reasons. In the meantime, the instrument was used in a productive program of ground-based observing, which collected excellent scientific data and served as instrument tests. Given here is an overview of the history of the SOUP program, the scientific discoveries, and the instrument design and performance
Quasi-periodic Fast-mode Wave Trains Within a Global EUV Wave and Sequential Transverse Oscillations Detected by SDO/AIA
We present the first unambiguous detection of quasi-periodic wave trains
within the broad pulse of a global EUV wave (so-called "EIT wave") occurring on
the limb. These wave trains, running ahead of the lateral CME front of 2-4
times slower, coherently travel to distances along the solar
surface, with initial velocities up to 1400 km/s decelerating to ~650 km/s. The
rapid expansion of the CME initiated at an elevated height of 110 Mm produces a
strong downward and lateral compression, which may play an important role in
driving the primary EUV wave and shaping its front forwardly inclined toward
the solar surface. The waves have a dominant 2 min periodicity that matches the
X-ray flare pulsations, suggesting a causal connection. The arrival of the
leading EUV wave front at increasing distances produces an uninterrupted chain
sequence of deflections and/or transverse (likely fast kink mode) oscillations
of local structures, including a flux-rope coronal cavity and its embedded
filament with delayed onsets consistent with the wave travel time at an
elevated (by ~50%) velocity within it. This suggests that the EUV wave
penetrates through a topological separatrix surface into the cavity, unexpected
from CME caused magnetic reconfiguration. These observations, when taken
together, provide compelling evidence of the fast-mode MHD wave nature of the
{\it primary (outer) fast component} of a global EUV wave, running ahead of the
{\it secondary (inner) slow} component of CME-caused restructuring.Comment: 17 pages, 12 figures; accepted by ApJ, April 24, 201
Vorticity and divergence in the solar photosphere
We have studied an outstanding sequence of continuum images of the solar granulation from Pic du Midi Observatory. We have calculated the horizontal vector flow field using a correlation tracking algorithm, and from this determined three scalar field: the vertical component of the curl; the horizontal divergence; and the horizontal flow speed. The divergence field has substantially longer coherence time and more power than does the curl field. Statistically, curl is better correlated with regions of negative divergence - that is, the vertical vorticity is higher in downflow regions, suggesting excess vorticity in intergranular lanes. The average value of the divergence is largest (i.e., outflow is largest) where the horizontal speed is large; we associate these regions with exploding granules. A numerical simulation of general convection also shows similar statistical differences between curl and divergence. Some individual small bright points in the granulation pattern show large local vorticities