An EUV Jet and Hα Filament Eruption Associated with Flux Cancelation in a Decaying Active Region

Using data from the Transition Region and Coronal Explorer (TRACE), Solar and Heliospheric Observatory (SOHO), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and Hida Observatory (HO), we present a detailed study of an EUV jet and the associated Hα filament eruption in a major flare in the active region NOAA 10044 on 29 July 2002. In the Hα line wings, a small filament was found to erupt out from the magnetic neutral line of the active region during the flare. Two bright EUV loops were observed rising and expanding with the filament eruption, and both hot and cool EUV plasma ejections were observed to form the EUV jet. The two thermal components spatially separated from each other and lasted for about 25 minutes. In the white-light corona data, a narrow coronal mass ejection (CME) was found to respond to this EUV jet. We cannot find obvious emerging flux in the photosphere accounting for the filament eruption and the EUV jet. However, significant sunspot decay and magnetic-flux cancelation owing to collision of opposite flux before the events were noticed. Based on the hard X-ray data from RHESSI, which showed evidence of magnetic reconnection along the main magnetic neutral line, we think that all of the observed dynamical phenomena, including the EUV jet, filament eruption, flare, and CME, should have a close relation to the flux cancelation in the low atmosphere.     

Comparison of Prominences in Hα and He II 304 Å

In this letter, we bring attention to prominences which show different morphology in H and Heii 304 Å, as observed simultaneously by BBSO and EIT on board SOHO. Those two lines have been thought to represent similar chromospheric structures although they are formed at significantly different temperatures. We give two examples representing two kinds of anomaly: (1) prominences showing strong H emissions in the lower part and strong Heii emissions in the upper part, and (2) erupting prominences showing extensive Heii emission, but nothing in H. Our results indicate that a part or the whole of a prominence may be too hot to emit H radiation, possibly due to heating or thermal instability. Please note that these are not just two isolated cases, many other prominences show the similar differences in H and Heii 304 Å.     

Filament Recognition and Image Cleaning on Meudon Hα Spectroheliograms

This paper presents the techniques developed for the automated detection of filaments on Meudon H spectroheliograms, and, by extension, on any full-disk H Sun observations. Some cleaning processes are first applied to the images to correct them from defects characteristic of the instrument. Indeed, these defects may lead to spurious detections. From the cleaned images, filament areas are then segmented using a region growing method which efficiently returns the full extent of these dark areas. The filaments are finally described by means of their pruned skeleton. This representation allows one to compare the automatically segmented filaments with those manually recorded for Meudon Synoptic Maps. The very good agreement observed on a representative set of images confirms that this method can effectively be used in the frame of the EGSO (European Grid of Solar Observations) project in order to produce a reliable catalog dedicated to solar features.     

Automatic Detection of Limb Prominences in 304 Å EUV Images

A new algorithm for automatic detection of prominences on the solar limb in 304 Å EUV images is presented, and results of its application to SOHO/EIT data discussed. The detection is based on the method of moments combined with a classifier analysis aimed at discriminating between limb prominences, active regions, and the quiet corona. This classifier analysis is based on a Support Vector Machine (SVM). Using a set of 12 moments of the radial intensity profiles, the algorithm performs well in discriminating between the above three categories of limb structures, with a misclassification rate of 7%. Pixels detected as belonging to a prominence are then used as the starting point to reconstruct the whole prominence by morphological image-processing techniques. It is planned that a catalogue of limb prominences identified in SOHO and STEREO data using this method will be made publicly available to the scientific community.     

Hα Emission and Dynamics in Groups of Galaxies

H_α luminosities of a sample of galaxies in nearby compactgroups are presented. Our purpose is to study the influence of thegroup environment on the star formation rates (SFRs) of the galaxies in thegroups, provided that the H_α luminosity is a good tracer of theSFR of disc galaxies. Measuring the global L /L _B of the groups – including early-type galaxies – we find that the average value of the H_α emission is not significantly different from thatmeasured for field galaxies, and that most of the groups that show thehighest level of L /L _B, with respect to a set of synthetic groups built out of field galaxies, show tidal features in at least one of their members. Finally, we have exploredthe relationship between the ratio L /L _B and severalrelevant dynamical parameters of the groups (velocity dispersion, crossingtime, radius and mass-to-luminosity ratio) and have found no clearcorrelation. This suggests that the exact dynamical state of a groupdoes not appear to control the SFR of the group as a whole. This revised version was published online in July 2006 with corrections to the Cover Date.     

High-Resolution Hα Observations of Proper Motion in NOAA 8668: Evidence for Filament Mass Injection by Chromospheric Reconnection

There have been two different kinds of explanations for the source of cool material in prominences or filaments: coronal condensations from above and cool plasma injections from below. In this paper, we present observational results which support filament mass injection by chromospheric reconnection. The observations of an active filament in the active region NOAA 8668 were performed on 17 August 1999 at a wavelength of H–0.6 Å using the 65 cm vacuum reflector, a Zeiss H birefringent filter, and a 12-bit SMD digital camera of Big Bear Solar Observatory. The best image was selected every 12 s for an hour based on a frame selection algorithm. All the images were then co-aligned and corrected for local distortion due to the seeing. The time-lapse movie of the data shows that the filament was undergoing ceaseless motion. The H flow field has been determined as a function of time using local correlation tracking. Time-averaged flow patterns usually trace local magnetic field lines, as inferred from H fibrils and line-of-sight magnetograms. An interesting finding is a transient flow field in a system of small H loops, some of which merge into the filament. The flow is associated with a cancelling magnetic feature which is located at one end of the loop system. Initially a diverging flow with speeds below 10 km s^–1 is visible at the flux cancellation site. The flow is soon directed along the loops and accelerated up to 40 km s^–1 in a few minutes. Some part of the plasma flow then merges into and moves along the filament. This kind of transient flow takes place several times during the observations. Our results clearly demonstrate that reconnection in the photosphere and chromosphere is a likely way to supply cool material to a filament, as well as re-organizing the magnetic field configuration, and, hence, is important in the formation of filaments.     

Hα and Hβ profile variations in the spectra of the star 55 Cyg

Profile variations in the H_α and H_β lines in the spectra of the star 55 Cyg are investigated from observations acquired in 2010 at the Cassegrain focus of the 2-m telescope at the Shamakhy Astrophysical Observatory after named N.Tusi (Azerbaijan). The spectral resolution is approximately 15000. The emission and absorption components of the Ha profile are found to disappear on some observational days, and one of the spectrograms exhibits an inverse P-Cyg profile of Hα. It is suggested that the observational evidence for the nonstationary atmosphere of 55 Cyg can be associated in part with nonspherical stellar wind.     

Electron acceleration and heating in solar flares: Interpretation of Hα signatures

Vector magnetogram, H, and hard X-ray observations of flares are reviewed which show that nonthermal electron signatures in H are never cospatial with regions of maximum current density for the small number of flares analyzed, but lie to the sides of these regions. By considering electron acceleration and transport requirements, four conditions are found that must be fulfilled to observe nonthermal electron signatures in H: (1) The plasma beta 0.3 in the acceleration region. (2) The energy flux of electrons above 20 keV is greater than 10¹⁰ erg cm^–2 s^–1. (3) The column densityN 10²⁰ cm^–2 between the electron source and the chromosphere. (4) The coronal pressure in the flux tube connecting to the H layerp 100 dyne cm^–2. Condition 2 can be most easily met in the initial stages of flares. In contrast, the only condition for a high-pressure H signature isp 1000 dyne cm^–2, which is most easily met in a region of maximum current density or heating and far enough into the flare for significant heating to have occurred. Thus, high-pressure signatures should be expected to occur more frequently than nonthermal electron signatures and to occur generally later in time.Also Guest Worker at NOAA Space Environment Laboratory Boulder Colorado U.S.A.     

Simultaneous measurements of the polarization in Hα and D3 prominence emissions

Simultaneous observations of the polarization of radiations H and D₃ have been performed in 1979 at Pic du Midi on 60 solar prominences (300 pairs of measurements). For the essential part of the sample, the degree of polarization p(D₃) does not depend strongly upon the intensity E(D₃); on the contrary p(H) decreases steeply when E(H) goes beyond the brightness which corresponds to (H) = 1 (Figure 4); the deviation of the polarization direction (H) does not show such a strong dependance upon E(H) (Figure 6). A crude estimate of the possible role of multiple scattering in an optically thick prominence is in general agreement with observational data but a detailed comparison will be possible only when a complete theory of the Hanle effect in non optically thin layers will be available.Therefore, H polarization measurements are presently useful mainly when (H) < 1 and, in connexion with D₃ measurements (Figure 8), they should make possible to determine the three components of the prominence magnetic vector. Prospects are given for the observation of other lines (H; 10 830 Å) which do not suffer heavy self-absorption effects and would be well-suited to this type of study.     

Hα and hard X-ray development in two-ribbon flares

Morphological features of two-ribbon flares have been studied, using simultaneous ISEE-3 hard X-ray records and high-resolution Big Bear H movies for more than 20 events. Long-lasting and complex hard X-ray bursts are almost invariably found associated with flares of the two-ribbon type. We find at least three events, namely March 31, 1979, April 10, 1980, and July 1, 1980, where the occurrence of individual spikes in hard X-ray radiation coincides with suddenly enhanced H emission covering the sunspot penumbra. There definitely exist important ( 1B) two-ribbon H flares without significant hard X-ray emission.     

Dynamic evolution of recurrent mass ejections observed in Hα and Civ lines

During a coordinated SMY program, the consecutive formation of two new active centers merging together within AR 2646 was observed from 28 August, to 5 September, 1980. The two preceding spots compressed an inverse polarity spot on 1 September 1980, causing recurrent ejecta of matter with time intervals around 10 min. The observations of the MSDP spectrograph operating in H at the Meudon Solar tower and of the UVSP spectrometer on SMM in the Civ 1548 Å line show that cold and hot material had the same projection, although the upward Civ velocity structure was more extended than the H one. We present evidence that observed contrasts of the H absorbing structure can be interpreted in terms of a dynamic cloud model overlying the chromosphere. H matter follows a magnetic channel with upward velocity around 20–30 km s^–1 in the first phase of the event and with downward velocity ( - 40 km s^–1) in the second phase. The stored energy is not sufficient to trigger a flare, nor even to propulse matter along the full length of an arch, because of the periodic reorganisation of the magnetic field.     

Spatial correlation of Hα filaments and photospheric velocity

The location of H filaments is compared with maps of the photospheric line of sight velocity V and the magnetic field H . It is found that (1) H filaments are associated with regions of ¦V ¦ 300m s^–1, (2) always both positive as well as negative velocities are present under H structures, (3) stable (long lasting) portion of filaments frequently occur at the position of H = 0 as well as V = 0 lines, (4) this association remains valid for the longitudes less than 50° from central meridian.     

Detection of Hα Intensity Oscillations in Solar Flares

We report here the first direct evidence for detection of H intensity oscillations in two extended flares of 15 November 1989 and 20 April 1991. The relative intensity variations measured with time at 18 different flare and chromospheric locations were analysed to obtain the oscillation modes. The analysis shows prominent 5- and 3-min modes in flares in addition to their existence in the chromosphere. However, there exists a frequency difference between the flare and chromospheric modes. This frequency deviation of about 300 µHz is proposed as an influence of higher magnetic field, location of the measurements (height) in chromosphere, and high temperature in the flare.     

Variability of the Hα emission in ϕPer

Photoelectric spectrum scans of the Be shell star Per in the H region have been taken to investigate the variations of H emission lines. Definite variations with time-scales of a few minutes have been detected. It is hoped that hydromagnetic instability within the envelope is responsible for such variations.     

Oscillations of the Hα emission in solar prominences

The time dependence of Doppler shift and line-center intensity is simultaneously observed for the H emission of three solar prominences, each one during about two hours. Doppler oscillations with periods near one hour and amplitudes between 1 and 2 km s^–1 are conspicuously visible in the recordings of all three prominences. Fourier analysis yields periods of 50, 60, and 64 min, as well as slight indications of short periods near 3 and 5 min. No oscillations are found in the line-center brightness.     

The Hβ Chromospheric Magnetic Field in a Quiescent Filament

We observed the line-of-sight magnetic field in the chromosphereand photosphere of a large quiescent filament on the solar disk on September 6, 2001 using the Solar Magnetic Field Telescope in Huairou Solar Observing Station. The chromospheric and photospheric magnetograms together with Hβ filtergrams of the filament were examined. The filament was located on the neutral line of the large scale longitudinal magnetic field in the photosphere and the chromosphere. The lateral feet of the filament were found to be related to magnetic structures with opposite polarities. Two small lateral feet are linked to weak parasitic polarity. There is a negative magnetic structure in the photosphere under a break of the filament. At the location corresponding to the filament in the chromospheric magnetograms, the magnetic strength is found to be about 40-70 Gauss (measuring error about 39 Gauss). The magnetic signal indicates the amplitude and orientation of the internal magnetic field in the filament. We discuss several possible causes which may produce such a measured signal. A twisted magnetic configuration inside the filament is suggested .     

High resolution observation of Hα solar flares and temporal relation between Hα and X-ray,microwave emission

We studied the evolutional characteristics of fine structures in H flare emitting regions and their relation to X-ray and microwave emissions for selected events observed with the 60 cm Domeless Solar Telescope at Hida Observatory, University of Kyoto. The principal conclusions of this investigation are: (1) H kernel consists of some finer bright points or Hflare points whose individual size is less than 1 arc sec. (2) Impulsive brightnenings of H flare points occurred simultaneously with the spikes of the hard X-ray and microwave bursts within the time resolution of our H observations which varied from 1 to 10 s. (3) It is concluded that fast electron beams must be the principal mechanism of heating H flares during the impulsive phase of a flare.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 265.     

Developing an Advanced Automated Method for Solar Filament Recognition and Its Scientific Application to a Solar Cycle of MLSO Hα Data

We developed a method to automatically detect and trace solar filaments in Hα full-disk images. The program is able not only to recognize filaments and determine their properties, such as the position, the area, the spine, and other relevant parameters, but also to trace the daily evolution of the filaments. The program consists of three steps: First, preprocessing is applied to correct the original images; second, the Canny edge-detection method is used to detect filaments; third, filament properties are recognized through morphological operators. To test the algorithm, we successfully applied it to observations from the Mauna Loa Solar Observatory (MLSO). We analyzed Hα images obtained by the MLSO from 1998 to 2009 and obtained a butterfly diagram of filaments. This shows that the latitudinal migration of solar filaments has three trends in Solar Cycle 23: The drift velocity was fast from 1998 to the solar maximum, after which it became relatively slow. After 2006, the migration became divergent, signifying the solar minimum. About 60 % of the filaments with latitudes higher than 50^° migrate toward the polar regions with relatively high velocities, and the latitudinal migrating speeds in the northern and the southern hemispheres do not differ significantly in Solar Cycle 23.     

Hα line emission and infrared excess in Be stars

The H observations of a selected sample of bright Be stars are presented. The available infrared observations at K band (2.2 m) of these stars have been used to find the infrared excess emission. The analysis of the combined data show thatL _H, the luminosity of the H emission line, is proportional toL _IR, the luminosity of the infrared excess emission. The linear correlation betweenL _IR andL _H shows that both the infrared excess and the H line originate in a common region. It is also detected that the infrared excess emission is produced throughout the whole envelope whereas the H is emitted in some defined region of the circumstellar (CS) envelope.     

Disparity between Hα and Hβ in SN 2008 in: Inhomogeneous external layers of type IIP supernovae?

We study disparity between Hα and Hβ in early spectra of the type IIP supernova SN 2008in. The point is that these lines cannot be described simultaneously in a spherically-symmetric model with the smooth density distribution. It is shown that an assumption of a clumpy structure of external layers of the envelope resolves the problem. We obtain estimates of the velocity at the inner border of the inhomogeneous zone (≈6100 km s^?1), the filing factor of inhomogeneities (≤0.5), and the mass of the inhomogeneous layers (～0.03 M _⊙). The amplitude of flux fluctuations in the early spectrum of Hα (ΔF/F ～ 10^?2) imposes a constraint on the size of inhomogeneities (≤200 km s^?1). A detection of fluctuations in the early Hα of type IIP supernovae might become an observational test of the inhomogeneous structure of their envelopes. We propose also the indirect test of the clumpy structure of external layers: the study of properties of the initial radiation outburst due to the shock breakout. The inhomogeneous structure of external layers of type IIP supernovae could be an outcome of density perturbations and density inversion in outer convective layers of presupernova red supergiant.