An empirical model has been developed to reproduce the drift of the spectrum recorded by the EIS on Hinode using instrumental temperatures and relative motion of the spacecraft. The EIS spectrum shows an artificial drift in wavelength dimension in sync with the revolution of the spacecraft, which is caused by temperature variations inside the spectrometer. The drift amounts to 70 km s −1 in Doppler velocity and introduces difficulties in velocity measurements. An artificial neural network is incorporated to establish a relationship between the instrumental temperatures and the spectral drift. This empirical model reproduces observed spectrum shift with an rms error of 4.4 km s −1 . This procedure is robust and applicable to any spectrum obtained with EIS, regardless of the observing field. In addition, spectral curvatures and spatial offset in the north -south direction are determined to compensate for instrumental effects.

The interaction between emerging magnetic flux and the pre-existing ambient field has become a "hot" topic for both numerical simulations and high-resolution observations of the solar atmosphere. The appearance of brightenings and surges during episodes of flux emergence is believed to be a signature of magnetic reconnection processes. We present an analysis of a small-scale flux emergence event in NOAA 10971, observed simultaneously with the Swedish 1-m Solar Telescope on La Palma and the Hinode satellite during a joint campaign in September 2007. Extremely high-resolution G-band, Hα, and Ca II H filtergrams, Fe I and Na I magnetograms, EUV raster scans, and Xray images show that the emerging region was associated with chromospheric, transition region and coronal brightenings, as well as with chromospheric surges. We suggest that these features were caused by magnetic reconnection at low altitude in the atmosphere. To support this idea, we perform potential and linear force-free field extrapolations using the FROMAGE service. The extrapolations show that the emergence site is cospatial with a 3D null point, from which a spine originates. This magnetic configuration and the overall orientation of the field lines above the emerging flux region are compatible with the structures observed in the different atmospheric layers, and remain stable against variations of the force-free field parameter. Our analysis supports the predictions of recent 3D numerical simulations that energetic phenomena may result from the interaction between emerging flux and the pre-existing chromospheric and coronal field.

Aims. We attempt to understand the driving mechanism of a macrospicule and its relationship with a coronal jet. Methods. We study the dynamics of a macrospicule and an associated coronal jet captured by multi-spacecraft observations. Doppler velocities in both the macrospicule and the coronal jet are determined by EIS and SUMER spectra. Their temporal evolution is studied using X-ray and He ii λ304 images.Results. A blueshift of −120 ± 15 km s −1 is detected on one side of the macrospicule, while a redshift of 50 ± 6 km s −1 is found at the base of the other side. The inclination angle of the macrospicule inferred from a stereoscopic analysis with STEREO suggests that the measured Doppler velocities can be attributed to a rotating motion of the macrospicule rather than a radial flow or an expansion. Conclusions. The macrospicule is driven by the unfolding motion of a twisted magnetic flux rope, while the associated X-ray jet is a radial outflow.

We present Hinode/EIS raster scan observations of the plage region taken during the gradual phase of the GOES X3.2 flare that occurred on 2006 December 13. The plage region is located 200${}^{\prime\prime}$ east of the flare arcade. The plage region has a small transient coronal hole. The transient coronal hole is strongly affected by an X-class flare, and upflows are observed at its boundary. Multi-wavelength spectral observations allow us to determine velocities from the Doppler shifts at different temperatures. Strong upflows along with stationary plasma have been observed in the Fe XV line 284.2 Å (log$T/$ K $=6.3$) in the plage region. The strong upflows reach almost 150 km s$^{-1}$, which was estimated by a two-component Gaussian fitting. On the other hand, at a lower corona/transition region temperature (He II, 256.3 Å, log$T/$ K $=$ 4.9), very weak upflows, almost stationary, have been observed. We find that these upflow velocities clearly depend on the temperature with the hottest line, Fe XV, showing the fastest upflow velocity and the second-highest line, Fe XIV, showing the second-highest upflow velocity (130 km s$^{-1}$). All velocities are below the sound speed. The trend of the upflow dependence on temperature dramatically changes at 1 MK. These results suggest that heating may have an important role for strong upflow.

Aims. We present a study of the temporal evolution of coronal loops in active regions and its implications for the dynamics in coronal loops. Methods. We analyzed images of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) at multiple temperatures to detect apparent motions in the coronal loops. Results. Quasi-periodic brightness fluctuations propagate upwards from the loop footpoint in hot emission at 1 MK, while sporadic downflows are seen in cool emission below 1 MK. The upward motion in hot emission increases just after the cool downflows. Conclusions. The apparent propagating pattern suggests a hot upflow from the loop footpoints, and is considered to supply hot plasma into the coronal loop, but a wavelike phenomenon cannot be ruled out. Coronal condensation occasionally happens in the coronal loop, and the cool material flows down to the footpoint. Emission from cool plasma could have a significant contribution to hot AIA channels in the event of coronal condensation.

The origin of the solar wind is one of the most important unresolved problems in space and solar physics. We report here the first spectroscopic signatures of the nascent fast solar wind on the basis of observations made by the EUV Imaging Spectrometer (EIS) on Hinode in a polar coronal hole, in which patches of blueshift are clearly present on dopplergrams of coronal emission lines with a formation temperature of lg(T /K) ≥6.0. The corresponding upflow is associated with open field lines in the coronal hole, and seems to start in the solar transition region and becomes more prominent with increasing temperature. This temperature-dependent plasma outflow is interpreted as evidence of the nascent fast solar wind in the polar coronal hole. The patches with significant upflows are still isolated in the upper transition region but merge in the corona, in agreement with the scenario of solar wind outflow being guided by expanding magnetic funnels.

Velocity structures of jets in a coronal hole have been derived for the first time.Hinode observations revealed the existence of many bright points in coronal holes. They are loop-shaped and sometimes associated with coronal jets. Spectra obtained with the Extreme ultraviolet Imaging Spectrometer (EIS) on board Hinode are analyzed to infer Doppler velocity of bright loops and jets in a coronal hole of the north polar region. Elongated jets above bright loops are found to be blue-shifted by 30 km s −1 at maximum, while foot points of bright loops are red-shifted. Blue-shifts detected in coronal jets are interpreted as upflows produced by magnetic reconnection between emerging flux and the ambient field in the coronal hole.

In this paper, we extend our earlier work to provide additional evidence for an alternative scenario to explain the nature of so-called 'explosive events'. The bi-directed, fast Doppler motion of explosive events observed spectroscopically in the transition region emission is classically interpreted as a pair of bidirectional jets moving upward and downward from a reconnection site. We discuss the problems of such a model. In our previous work, we focused basically on the discrepancy of fast Doppler motion without detectable motion in the image plane. We now suggest an alternative scenario for the explosive events, based on our observations of spectral line tilts and bifurcated structure in some events. Both features are indicative of rotational motion in narrow structures. We explain the bifurcation as the result of rotation of hollow cylindrical structures and demonstrate that such a sheath model can also be applied to explain the nature of the puzzling 'explosive events'. We find that the spectral tilt, the lack of apparent motion, the bifurcation, and a rapidly growing number of direct observations support an alternative scenario of linear, spicular-sized jets with a strong spinning motion.