NIXT

Abstract: We analyze and compare five coronal regions simultaneously observed by NIXT and Yohkoh/SXT on April 12, 1993. The compact loop structures (length ∼ 109 cm) imaged in three regions with NIXT and with SXT have a good general morphological correspondence. A large scale ( ≈ 1.7×1010 cm) and an intermediate scale ( ≈ 5 × 109 cm) structure observed in the NIXT image have no obvious counterpart in the SXT image. The pressure of the loop plasma detected by NIXT is derived from the brightness profile along the loops by applying a method based on loop models. The pressure of the loop plasma in the SXT band has also been derived from loop models on the basis of the temperature obtained from the standard Yohkoh data analysis. NIXT pressures are systematically lower than those found with SXT. By comparing the measured total loop luminosity to that expected on the basis of loop models, we constrain quantitatively the volume filling factor of the plasma emitting respectively in the NIXT and SXT bands. The filling factors obtained in the NIXT band for the compact and intermediate loops are very low ( 10−3−10−2), but they are of the order of unity for the large structure. The low filling factors suggest a strong loop filamentation. The filling factors for the compact structures are instead of the order of unity in the SXT band. We discuss our results and propose a scenario for their interpretation.

Abstract: The authors describe an XUV detector with a spatial resolution of approximately=6 mu m designed to fly on the normal incidence X-ray telescope (NIXT) rocket package. The telescope is a 10 in (254 mm) diameter Ritchey-Chretien system which relies on unusually high accuracy multilayer coatings to image active regions on the Sun. The coatings are reflective in a narrow band centred on a wavelength near 6.3 nm; thus the detector's jog is to convert the XUV image into an electronic format which can be stored on tape or relayed to the ground via telemetry. The authors are primarily concerned with how the X-rays are converted into a very high resolution visible light image which can be sensed and read out by the image processing electronics.

Abstract: Progress in x-ray optics, beginning in the 1960’s and continuing to the present day, has been intimately tied to progress in our understanding of the coronae of the Sun and of solar-like stars. Innovative instrumentation, first used on sounding rockets and then flown on satellites, has been the most productive route for progress. This paper presents an overview of the status of coronal x-ray imaging research at the time that Skylab was launched in 1973, and of the contributions made by Skylab and by the Einstein Observatory. We then discuss the new technique of multilayer imaging for soft x-rays and the contributions which the NIXT experiment is making to our understanding of the structuring and heating of the corona.

Abstract: Results obtained during the June 23, 1988 flight of the normal incidence X-ray telescope (NIXT) sounding rocket payload are reported. The telescope primary is 25 cm in diameter, in a 750 cm e.f.l. (f/30) Ritchey-Chretien configuration, with multilayer coatings on the optics designed to image the Fe XVI and Mg X coronal emission lines near 63.5 A. Images of the onset phase of a large (M8) Solar flare were recorded during the flight on a modified T-max 400 film manufactured by Kodak. Some of the results obtained by comparison of the NIXT data with ground-based observations of the sun obtained simultaneously to the flight are also reported.