Abstract:The Hinode satellite (formerly Solar-

The X-ray Telescope (XRT) of the Hinode mission provides an unprecedented combination of spatial and temporal resolution in solar coronal studies. The high sensitivity and broad dynamic range of XRT, coupled with the spacecraft’s onboard memory capacity and the planned downlink capability will permit a broad range of coronal studies over an\ud extended period of time, for targets ranging from quiet Sun to X-flares. This paper discusses in detail the design, calibration, and measured performance of the XRT instrument up to the focal plane. The CCD camera and data handling are discussed separately in a companion paper

Coronal magnetic fields are dynamic, and field lines may misalign, reassemble, and release energy by means of magnetic reconnection. Giant releases may generate solar flares and coronal mass ejections and, on a smaller scale, produce x-ray jets. Hinode observations of polar coronal holes reveal that x-ray jets have two distinct velocities: one near the Alfvén speed ( approximately 800 kilometers per second) and another near the sound speed (200 kilometers per second). Many more jets were seen than have been reported previously; we detected an average of 10 events per hour up to these speeds, whereas previous observations documented only a handful per day with lower average speeds of 200 kilometers per second. The x-ray jets are about 2 x 10(3) to 2 x 10(4) kilometers wide and 1 x 10(5) kilometers long and last from 100 to 2500 seconds. The large number of events, coupled with the high velocities of the apparent outflows, indicates that the jets may contribute to the high-speed solar wind.

Masuda et al. found a hard X-ray source well above a soft X-ray loop in impul sive compact-loop flares near the limb. This indicates that main energy release is going on above the soft X-ray loop, and suggests magnetic reconnection occurring above the loop, similar to the classical model for two ribbon flares. If the reconnection hypothesis is correct, a hot plasma (or plasmoid) ejection is expected to be associated with these flares. Using the images taken by the soft X-ray telescope aboard Yohkoh, we searched for such plasma ejections in eight impulsive compact-loop flares near the limb, which are selected in an unbiased manner and include also the Masuda flare, 1992 January 13 flare. We found that all these flares were associated with X-ra y plasma ejections high above the sof t X-ra y loop and the velocity of ejections is within the range of 50-400 km s Ϫ1. This result gives further support for magnetic reconnection hypothesis of these impulsive compact-loop flares.

Coronal jets represent important manifestations of ubiquitous solar transients, which may be the source of significant mass and energy input to the upper solar atmosphere and the solar wind. While the energy involved in a jet-like event is smaller than that of "nominal" solar flares and coronal mass ejections (CMEs), jets share many common properties with these phenomena, in particular, the explosive magnetically driven dynamics. Studies of jets could, therefore, provide critical insight for understanding the larger, more complex drivers of the solar activity. On the other side of the size-spectrum, the study of jets could also supply important clues on the physics of transients close or at the limit of the current spatial resolution such as spicules. Furthermore, jet phenomena may hint to basic process for heating the corona and accelerating the solar wind; consequently their study gives us the opportunity to attack a broad range of solar-heliospheric problems.Comment: 53 pages, 24 figure

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We have found 100 X-ray jets in the database of full Sun images taken with the Soft X-ray Telescope (SXT) aboard Yohkoh during the period from 1991 November through 1992 April. A statistical study for these jets results in the following characteristics: 1) Most are associated with small flares (microflaressubflares) at their footpoints. 2) The lengths lie in the range of a few × 104−4 × 105 km. 3) The widths are 5 × 103–105 km. 4) The apparent velocities are 10–1000 km s−1 with an average velocity of about 200 km s−1 . 5) The lifetime of the jet extends to ˜ 10 hours and the distribution of the observed lifetime is a power law with an index of ˜ 1.2. 6) 76% of the jets show constant or converging shapes; the width of the jet is constant or decreases with distance from the foot point. The converging type tends to be generated with an energetic foot point event and the constant type by a wide energy range of the footpoint event. 7) Many jets (˜ 68%) appear in or near to active regions (AR). Among the jets ejected from bright-point like features in ARs, most (˜ 86%) are observed to the west of the active region. 8) 27% of the jets show a gap ( > 104 km) between the exact footpoint of the jet and the brightest part of the associated flare. 9) The X-ray intensity distribution along an X-ray jet often shows an exponential decrease with distance from the footpoint. This exponential intensity distribution holds from the early phase to the decay phase.

We present the results of a statistical study of a large number of solar prominence events (PEs) observed by the Nobeyama Radioheliograph. We studied the association rate, relative timing and spatial correspondence between PEs and coronal mass ejections (CMEs). We classified the PEs as radial and transverse, depending on whether the prominence moved predominantly in the radial or horizontal direction. The radial events were faster and attained a larger height above the solar surface than the transverse events. Out of the 186 events studied, 152 (82%) were radial events, while only 34 (18%) were transverse events. Comparison with white-light CME data revealed that 134 (72%) PEs were clearly associated with CMEs. We compare our results with those of other studies involving PEs and white light CMEs in order to address the controversy in the rate of association between CMEs and prominence eruptions. We also studied the temporal and spatial relationship between prominence and CME events. The CMEs and PEs seem to start roughly at the same time. There was no solar cycle dependence of the temporal relationship. The spatial relationship was, however, solar cycle dependent. During the solar minimum, the central position angle of the CMEs had a tendency to be offset closer to the equator as compared to to that of the PE, while no such effect was seen during solar maximum.