ROSA - Rapid Oscillations in the Solar Atmosphere

ROSA is a high cadence, high efficiency solar imager which is installed as a common-user instrument on the Dunn Solar Telescope at the National Solar Observatory in New Mexico, USA. Initially commissioned on the telescope in August 2008, ROSA has since provided data for high-impact publications appearing in a wealth of international peer-reviewed journals. ROSA has the ability to be used alongside the Hydrogen-Alpha Rapid Dynamics camera (HARDcam) to maximise chromospheric imaging capabilities. It is capable of observing the Sun's atmosphere simultaneously in six bandpasses, with typical characteristics of:

  • Two-pixel spatial resolution = 84km @ 351nm, 95km @ Ca II K, 141km @ Na I D1, 158km @ H-alpha
  • Temporal resolution = 30.3 frames-per-second maximum

If you are interested in making use of ROSA you should contact Mihalis Mathioudakis, David Jess, or Peter Keys for information and advice.

Sample ROSA images

The sample ROSA snapshots shown below are designed to show the capabilities of the imaging system. The diffraction-limited field-of-view is approximately 70“ x 70”, but can be increased depending on the requirements of the observer. Please click on the images below to see full-size versions and/or play the respective movies.

Processing Pipeline

These movies are prepared to show the various stages of data reduction required to produce a final, science-ready data product. The first movie is a time series which has only been calibrated using dark subtraction and flat fielding. The second movie reveals the same time series, but now only speckle reconstructed. It is clear that while the spatial resolution has been drastically improved, small-scale turbulent fluctuations are still visible in the time series producing a “watery” effect. The final movie displays the fully-calibrated image sequence, consisting of dark subtracted, flat fielded, speckle reconstructed, and de-stretched consecutive images. This is a “science ready” data product according to the data reduction pipeline written by David Jess.

Larger field-of-view of an Active Region

These images were acquired on the 07-Mar-2013, and consist of the G-band (upper left; 30.3 FPS), Na I D1 core (upper right; 15.15 FPS), Ca II K (lower left; 27 FPS), and the H-alpha core (lower right; 28 FPS). The G-band and Na I D1 images were acquired by ROSA, while the H-alpha and Ca II K images were obtained simultaneously by the HARDcam and DJCcam instruments, respectively. Here, the field-of-view has been increased to 120“ x 120” (instead of the default 70“ x 70”) in order to capture an entire active region as it crossed the solar disk.

Comparison with SDO/AIA field-of-view

These images were acquired on the 13-Jul-2011, and consist of an SDO/AIA 171 Angstrom image (upper left), with dashed white lines indicating the typical diffraction-limited ROSA field-of-view. The upper-right panel shows an interlaced SDO/AIA 4500 Angstrom and ROSA blue continuum image. The lower panels reveal the ROSA blue continuum (left) and HARDcam H-alpha core (right) images interlaced with a simultaneous SDO/AIA 171 Angstrom snapshot. Taken from Jess et al., ApJ, 757, 160 (2012)

Diffraction-limited Quiet Sun Observations

These images reflect heights of 50-2000 km above the solar surface. The smallest structures that can be resolved have dimensions of around 100 km, and are associated with strong magnetic field concentrations (upper right) which burst out from the Sun's interior. The bubbling appearance of G-band (upper left) images is a result of hot gas rising and expanding, while reversed granulation is visible as a web-like structure through a singly-ionized Ca II filter (lower left). Bright points correspond to areas of intense magnetic fields which expand as they rise from the surface into the outer reaches of the solar chromosphere (H-alpha; lower right). Further information on these observations can be found in a series of papers:

28may2009_fov_bw.jpg

The Solar Cauldron

The first movie is a time lapse movie of the Sun's turbulent and dynamic chromosphere. An hour-long imaging sequence was acquired through a narrowband H-alpha filter at 656.3nm, revealing the evolution of a 40,000 x 40,000 square kilometer area on our nearest star (only 0.03% of the entire solar surface). These images, acquired using the ROSA system, provide unprecedented views of the periodic swaying and buffeting of magnetic field lines, as indicated by the dark straw-like structures present all over the field-of-view. Incredibly, these phenomena dislay supersonic motion, with velocities exceeding 30 km/s. The second movie is an identical time lapse movie, only interlaced with the corresponding (and simultaneous) photospheric G-band time series (red). The bubbling surface nature of our nearest star demonstrates exploding pockets of gas as they expand outwards from the Sun's interior. Intense magnetic fields manifest as bright points, visible as luminous specks on the Sun's surface, and connect upwards into the solar chromosphere. Taken from Jess et al., ApJ, 744, L5 (2012)

Useful documents

The ROSA Archive

A list of ROSA data which has been acquired and processed is available from this link.

Publications

public/research_areas/solar_physics/rosa.txt · Last modified: 2016/04/13 14:05 by Peter Keys

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