Archive for February, 2013
We are currently experiencing some technical difficulties with our main Helioviewer server. While we work on fixing it, we have moved all helioviewer.org services over to our backup server. All normal helioviewer.org services should be operating nominally. Please contact us if you notice anything amiss with helioviewer.org. JHelioviewer services are currently not operational, but we hope to have these up and running as soon as possible. Near real-time AIA and HMI images should be available as usual; streams of images from SOHO, STEREO and PROBA2 should be back to near real-time within 24 hours.
We apologize for the interruption to Helioviewer services, and we thank you for your patience.
We are happy to announce the availability of full disk Yohkoh Soft X-ray Telescope (SXT) images on helioviewer.org. SXT images x-rays from the Sun, and therefore looked at some of the hottest plasmas on the Sun. These data are important in trying to understand solar flares and the heating of the Sun’s corona.
Yohkoh (“Sunshine”) was launched in August 30, 1991, from the Kagoshima Space Center (Uchinoura) in Japan, and was a project of the Japanese Institute of Space and Astronautical Science (ISAS). The scientific objective was to observe the energetic phenomena taking place on the Sun, specifically solar flares in x-ray and gamma-ray emissions.
Yohkoh carried four instruments to detect energetic emissions from the Sun: the Soft X-Ray Telescope (SXT), the Hard X-Ray Telescope (HXT), the Bragg Crystal Spectrometer (BCS) and the Wide Band Spectrometer (WBS). A team from the United States collaborated on SXT, and teams from the United States and the United Kingdom collaborated on BCS.
SXT imaged X-rays in the 0.25 – 4.0 keV range. SXT used thin metallic filters to acquire images in restricted portions of the energy range. We are making images from the thin aluminium filter (thin-Al), and the aluminium-magnesium-manganese filter (AlMgMn) available. White-light images are also available up until November 1992. An example thin-aluminium image is shown below.
SXT could resolve features down to 2.5 arc seconds in size. Information about the temperature and density of the plasma emitting the observed x-rays was obtained by comparing images acquired with the different filters. Flare images could be obtained every 2 seconds. Smaller images with a single filter could be obtained as frequently as once every 0.5 seconds.
Yohkoh ceased operations on December 14, 2001. The SXT images we are making available cover portions of Solar Cycles 22 and 23 (we are currently somewhere close to the maximum of Solar Cyce 24). This historical data allows us to compare current solar behavior to previous solar behavior. Such studies allow us to better understand how the Sun operates on timescales of decades and longer.
Yohkoh SXT images are the first images of soft X-ray data available on helioviewer.org. We hope you enjoy examining this different view of the Sun on helioviewer.org.
Maintenance operations on the Helioviewer server are now complete, ahead of schedule. All Helioviewer services should be up and running as normal. We thank you for your patience in the last three days while our maintenance operations were ongoing. Please contact us if you notice a departure from normal services.