Hinode/SOHO campaign 7197 is the most extensive study of polar jet formation and evolution from within both the north and south polar coronal holes so far. For the first time, this study showed that the appearance of X-ray jets in the solar coronal holes occurs at very high frequency-about 60 jets d 1 on average. Using observations collected by the X-Ray Telescope on Hinode, a number of physical parameters from a large sample of jets were statistically studied. We measured the apparent outward velocity, the height, the width and the lifetime of the jets. In our sample, all of these parameters show peaked distributions with maxima at 160 km s 1 for the outward velocity, 5 10 4 km for the height, 8 10 3 km for the width, and about 10 min for the lifetime of the jets. We also present the first statistical study of jet transverse motions, which obtained transverse velocities of 0-35 km s 1. These values were obtained on the basis of a larger (in terms of frequency) and better sampled set of events than what was previously statistically studied (Shimojo et al. 1996, PASJ, 48, 123). The results were made possible by the unique characteristics of XRT. We describe the methods used to determine the characteristics and set some future goals. We also show that despite some possible selection effects, jets preferably occur inside the polar coronal holes.

Abstract.Modern solar telescope design in the EUV to x-ray range is now capable of producing large images in multiple channels at rapid cadences, with high spatial and temperature resolution. We discuss reconstruction of differential emission measures for solar coronal plasma using two state-of-the-art instruments: the X-Ray Telescope on Solar-B, and the Atmospheric Imaging Assembly on the Solar Dynamics Observatory. We discuss the relative merits of iteration and direct inversion methods for determining DEM(T ). We also consider strategies for automating and visualizing DEM maps, given the high data rates that these instruments will produce. We touch on the scientific potential of high-cadence, spatially resolved DEM data products.

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We present multi-wavelength observations of the evolution of the sheared magnetic fields in NOAA Active Region 10930, where two X-class flares occurred on 2006 December 13 and December 14, respectively. Observations made with the X-ray Telescope (XRT) and the Solar Optical Telescope (SOT) aboard Hinode suggest that the gradual formation of the sheared magnetic fields in this active region is caused by the rotation and west-to-east motion of an emerging sunspot. In the pre-flare phase of the two flares, XRT shows several highly sheared X-ray loops in the core field region, corresponding to a filament seen in the TRACE EUV observations. XRT observations also show that part of the sheared core field erupted, and another part of the sheared core field stayed behind during the flares, which may explain why a large part of the filament is still seen by TRACE after the flare. About 2–3 hours after the peak of each flare, the core field becomes visible in XRT again, and shows a highly sheared inner and less-sheared outer structure. We also find that the post-flare core field is clearly less sheared than the pre-flare core field, which is consistent with the idea that the energy released during the flares is stored in the highly sheared fields prior to the flare.

To understand the physical mechanisms for activity and heating in the solar atmosphere, the magnetic coupling from the photosphere to the corona is an important piece of information from the Hinode observations, and therefore precise positional alignment is required among the data acquired by different telescopes. The Hinode spacecraft and its onboard telescopes were developed to allow us to investigate magnetic coupling with co-alignment accuracy better than 1 arcsec. Using the Mercury transit observed on 8 November 2006 and co-alignment measurements regularly performed on a weekly basis, we have determined the information necessary for precise image co-alignment and have confirmed that co-alignment better than 1 arcsec can be realized between Solar Optical Telescope (SOT) and X-Ray Telescope (XRT) with our baseline co-alignment method. This paper presents results from the calibration for precise coalignment of CCD images from SOT and XRT.