69 research outputs found
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
High resolution studies of sunspots and flux tubes
This contract is for a three-year research study of sunspots and magnetic flux tubes in the solar atmosphere, using tunable filter images collected with a CCD camera during observing runs at the Canary Islands observatories in Spain. The best observations are analyzed and compared with theoretical models, to study the structure and dynamics of sunspots, their connections with surrounding magnetic fields, and the properties and evolution of smaller flux tubes in plage and quiet sun. Scientific results are reported at conferences and published in the appropriate journals. The contract is being performed by the Solar and Astrophysics Laboratory, part of the Lockheed Palo Alto Research Laboratory (LPARL) of the Research and Development Division (RDD) of Lockheed Missiles and Space Co., Inc. (LMSC). The principal investigator is Dr. Alan Title, and the research is done by him and other scientific staff at LPARL and Solar Physics Research Corporation (SPRC), often in collaboration with visiting scientists and students from other institutions. Highlights during this reporting period include completing the final version of a paper on the Evershed effect, writing a paper on magnetic diffusion, continuing work on contrast of small flux tubes, and work on the development of new models to interpret our sunspots observations
Observations and modeling of the early acceleration phase of erupting filaments involved in coronal mass ejections
We examine the early phases of two near-limb filament destabilization
involved in coronal mass ejections on 16 June and 27 July 2005, using
high-resolution, high-cadence observations made with the Transition Region and
Coronal Explorer (TRACE), complemented by coronagraphic observations by Mauna
Loa and the SOlar and Heliospheric Observatory (SOHO). The filaments' heights
above the solar limb in their rapid-acceleration phases are best characterized
by a height dependence h(t) ~ t^m with m near, or slightly above, 3 for both
events. Such profiles are incompatible with published results for breakout,
MHD-instability, and catastrophe models. We show numerical simulations of the
torus instability that approximate this height evolution in case a substantial
initial velocity perturbation is applied to the developing instability. We
argue that the sensitivity of magnetic instabilities to initial and boundary
conditions requires higher fidelity modeling of all proposed mechanisms if
observations of rise profiles are to be used to differentiate between them. The
observations show no significant delays between the motions of the filament and
of overlying loops: the filaments seem to move as part of the overall coronal
field until several minutes after the onset of the rapid-acceleration phase.Comment: ApJ (2007, in press
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
First High-resolution Spectroscopic Observations of an Erupting Prominence Within a Coronal Mass Ejection by the Interface Region Imaging Spectrograph (IRIS)
Spectroscopic observations of prominence eruptions associated with coronal
mass ejections (CMEs), although relatively rare, can provide valuable plasma
and 3D geometry diagnostics. We report the first observations by the Interface
Region Imaging Spectrograph (IRIS) mission of a spectacular fast CME/prominence
eruption associated with an equivalent X1.6 flare on 2014 May 9. The maximum
plane-of-sky and Doppler velocities of the eruption are 1200 and 460 km/s,
respectively. There are two eruption components separated by ~200 km/s in
Doppler velocity: a primary, bright component and a secondary, faint component,
suggesting a hollow, rather than solid, cone-shaped distribution of material.
The eruption involves a left-handed helical structure undergoing
counter-clockwise (viewed top-down) unwinding motion. There is a temporal
evolution from upward eruption to downward fallback with less-than-free-fall
speeds and decreasing nonthermal line widths. We find a wide range of Mg II k/h
line intensity ratios (less than ~2 expected for optically-thin thermal
emission): the lowest ever-reported median value of 1.17 found in the fallback
material and a comparably high value of 1.63 in nearby coronal rain and
intermediate values of 1.53 and 1.41 in the two eruption components. The
fallback material exhibits a strong () linear correlation between
the k/h ratio and the Doppler velocity as well as the line intensity. We
demonstrate that Doppler dimming of scattered chromospheric emission by the
erupted material can potentially explain such characteristics.Comment: 12 pages, 6 figures, accepted by ApJ (Feb 15, 2015
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
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