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.

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.

The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray-emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to approximately 1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun.

We consider the relationship between two flare-associated waves, a chromospheric Moreton wave and a coronal EIT wave, based on an analysis of an X-class flare event in AR 8100 on 1997 November 4. A Moreton wave was observed in $\mathrm{H}\alpha$, $\mathrm{H}\alpha {+} 0.8\,$$Å$, and $\mathrm{H}\alpha-0.8\,$$Å$ with the Flare-Monitoring Telescope (FMT) at the Hida Observatory. An EIT wave was observed in EUV with the Extreme ultraviolet Imaging Telescope (EIT) on board SOHO. The propagation speeds of the Moreton wave and the EIT wave were approximately $715 \,\mathrm{km} \,\mathrm{s}^{-1}$ and $202 \,\mathrm{km} \,\mathrm{s}^{-1}$, respectively. The times of visibility for the Moreton wave did not overlap those of the EIT wave, but the continuation of the former is indicated by a filament oscillation. Data on the speed and location clearly show that the Moreton wave differed physically from the EIT wave in this case. The Moreton wave preceded the EIT wave, which is inconsistent with an identification of the EIT wave with a fast-mode MHD shock.

In this paper we compare EUV Imaging Telescope (EIT) waves with simultaneous phenomena seen in H in order to address the question of what an EIT wave is. We surveyed the events associated with solar flares larger than GOES M-class in 1999-2002. The H data are taken with the Flare-monitoring Telescope (FMT) at the Hida Observatory of Kyoto University. Among 14 simultaneous observations of EIT waves and H, 11 were found to have filament eruptions, three were associated with Moreton waves, and one was found to have only filament oscillations. This shows that we cannot see clear wave fronts in H even if EIT waves exist, but that it is possible to recognize invisible waves by means of filament oscillations. The nature of filament oscillations and Moreton waves associated with EIT waves is examined in detail, and it is found that the filament oscillations were caused by EIT waves.

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Magnetic reconnection of solar coronal loops is the main process that causes solar flares and possibly coronal heating. In the standard model, magnetic field lines break and reconnect instantaneously at places where the field mapping is discontinuous. However, another mode may operate where the magnetic field mapping is continuous but shows steep gradients: The field lines may slip across each other. Soft x-ray observations of fast bidirectional motions of coronal loops, observed by the Hinode spacecraft, support the existence of this slipping magnetic reconnection regime in the Sun's corona. This basic process should be considered when interpreting reconnection, both on the Sun and in laboratory-based plasma experiments.

Routine ultraviolet imaging of the Sun’s upper atmosphere shows the spectacular manifestation of solar activity; yet, we remain blind to its main driver, the magnetic field. Here, we report unprecedented spectropolarimetric observations of an active region plage and its surrounding enhanced network, showing circular polarization in ultraviolet (Mg iih & k and Mn i) and visible (Fe i) lines. We infer the longitudinal magnetic field from the photosphere to the very upper chromosphere. At the top of the plage chromosphere, the field strengths reach more than 300 G, strongly correlated with the Mg iik line core intensity and the electron pressure. This unique mapping shows how the magnetic field couples the different atmospheric layers and reveals the magnetic origin of the heating in the plage chromosphere.