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* News 04/04/20 * The archive is using a new backend database. This has thrown up a few SQL errors in the last few days. If you have any issues please email adavey@nso.edu with either the number of eprint you are trying to edit or a link to your preprint.

Solar Cycle Variation of Coronal Temperature, Emission Measure, and Soft X-ray Irradiance Observed with Yohkoh Soft X-ray Telescope  

Aki Takeda   Submitted: 2019-12-03 20:28

This paper presents the solar soft X-ray irradiance(0.3-3.0nm) obtained from the mission-long full-Sun X-ray images observed with the Soft X-ray Telescope(SXT) of the Yohkoh mission(1991-2001). The irradiance was calculated using filter-ratio temperatures and emission measures from the full-Sun integrated X-ray signals employing a coronal spectrum synthesized with CHIANTI atomic database version 8.0. Dependence of the results on the assumption of elemental abundances is investigated. The SXT irradiance for a shorter wavelength range was also calculated and compared with the low energy flux(0.1-0.8nm) of the X-Ray Sensor(XRS) aboard the GOES satellite. To incorporate the spatial information of the observed corona, we tried the alternative method to derive irradiance by applying the filter ratio method to the images of Northern hemispheric corona instead of spatially integrated signals from there. The emission-measure weighted average of the spatially resolved temperatures turned out to be generally 20 to 30% lower than those derived from the integrated signals, while the total of spatially resolved emission measures are accordingly 1.5 to 2 times higher. This trend is enhanced when solar activity is the lowest in early 1996. The irradiance obtained from the alternative method does not significantly vary from the result from the integrated signals. This provides some validation for the simpler full-Sun integrated method. The temporal variation of the emission measures of cool(<1.5MK), medium and hot(>2.5MK) components indicates that the ratio of the hot component relative to the medium component is higher in the ascending phase(mid 1998-2001) than the descending phase(1992-1995) of the solar activity cycle.

Authors: Aki Takeda, Loren Acton, and Nicole Albanese
Projects: Yohkoh-SXT

Publication Status: Accepted in the ApJ
Last Modified: 2019-12-04 11:30
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The Hinode /XRT Full-Sun Image Corrections and the Improved Synoptic Composite Image Archive  

Aki Takeda   Submitted: 2015-12-27 22:14

The XRT Synoptic Composite Image Archive (SCIA) is a storage and gallery of X-ray full-Sun images obtained through the synoptic program of the X-Ray Telescope (XRT) onboard the Hinode satellite. The archived images provide a quick history of solar activity through the daily and monthly layout pages and long-term data for morphological and quantitative studies of the X-ray corona. This article serves as an introduction to the SCIA, i.e., to the structure of the archive and specification of the data products included therein. We also describe a number of techniques used to improve the quality of the archived images: preparation of composite images to increase intensity dynamic range, removal of dark spots that are due to contaminants on the CCD, and correction of the visible stray light contamination that has been detected on the Ti-poly and C-poly filter images since May 2012.

Authors: Takeda, A., Yoshimura, K., Saar, S.
Projects: Hinode/XRT

Publication Status: SolarPhysics(in press)
Last Modified: 2015-12-30 12:41
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Characteristics of the Re-Calculated Yohkoh/SXT Temperature Response  

Aki Takeda   Submitted: 2011-08-03 22:50

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Aki Takeda
Projects: Yohkoh-SXT

Publication Status: Solar Physics (in press)
Last Modified: 2011-08-04 08:32
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Abstracts by Author
Solar Cycle Variation of Coronal Temperature, Emission Measure, and Soft X-ray Irradiance Observed with Yohkoh Soft X-ray Telescope
The Hinode /XRT Full-Sun Image Corrections and the Improved Synoptic Composite Image Archive
Characteristics of the Re-Calculated Yohkoh/SXT Temperature Response

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