First Simultaneous Observation of Hα Moreton Wave, EUV Wave, and Filament/Prominence Oscillations

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1 AA: 211/9/14 First Simultaneous Observation of Hα Moreton Wave, EUV Wave, and Filament/Prominence Oscillations Ayumi Asai 1, Takako T. Ishii 2, Hiroaki Isobe 1, Reizaburo Kitai 2, Kiyoshi Ichimoto 2, Satoru UeNo 2, Shin ichi Nagata 2, Satoshi Morita 2, Keisuke Nishida 2, Daikou Shiota 3, Akihito Oi 4, Maki Akioka 5, and Kazunari Shibata 2 asai@kwasan.kyoto-u.ac.jp ABSTRACT (no more than 25 words for ApJL) We observed a Moreton wave associated with an X6.9 flare that occurred on 211 Augst 9 at the active region NOAA We discuss the features in detail. (EIT wave) Subject headings: Magnetohydrodynamics (MHD) Shock waves Sun: corona Sun: filaments, prominences Sun: flare 1. Introduction (no more than 35 words for ApJL) Moreton waves, flare-associated waves seen in Hα, have been observed (Moreton 196; Smith & Harvey 1971) to propagate in restricted angles with the velocity of about 5 15 km s 1. They sometimes show arc-shaped fronts, and are often associated with type-ii radio bursts (Kai 197). They are very transient, and apeear only for about 1 minutes or so. Associated with flares, remote filaments are sometimes activated or oscillated. These winking 1 Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto , Japan. 2 Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto , Japan. 3 Advanced Science Institute, RIKEN (Institute of Physics and Chemical Research), Wako, Saitama , Japan. 4 Department of Science, Ibaraki University, Mito, Ibaraki , Japan. 5 Hiraiso Solar Observatory, National Institute of Information and Communications Technology, Hitachinaka, Ibaraki , Japan.

2 2 filaments are also thought to be caused by flare-associated waves, and are called as invisible Moreton waves Smith & Harvey (1971); Tripathi et al. (29). Shortly after the findings, Uchida (1968, 197, 1974) suggested that Moreton waves are the intersection of the fast mode magnetohydrodynamic (MHD) shock propagating in the cornea with chromosphere. This model has been widely accepted, and the coronal counterparts have been surveyed for a few decades. After the launch of the Solar and Heliospheric Observatory (SOHO), the EUV Imaging Telescope (EIT) found wavelike phenomena associated with flares, which are called EIT waves Thompson et al. (1999, 2). Although EIT waves were expected to be the coronal counterpart of Moreton waves, they show different physical characteristics from those of Moreton waves: the propagating velocity is much slower than that of Moreton wave and is about 2 4 km s 1, the lifetime is much longer and is about 45 6 minutes, they propagate isotropically, while Moreton waves propagate with restricted angles (Klassen et al. 2; Warmuth 27). There have been, therefore, remained a question whether EIT waves are really coronal counterparts of Moreton waves or no. As for searching for a coronal counterpart of Moreton waves, Yohkoh/ the Soft X-ray Telescope (SXT) found wavelike phenomena in soft X-rays, called X-ray waves (Khan & Hudson 2; Khan & Aurass 22). X-ray waves are confirmed to be a real counterpart of Moreton waves by simultaneous observations of X-ray waves and Hα Moreton waves (Narukage et al. 22, 24). Coronal X-ray waves and EUV waves have been also observed spectroscopically with the EUV Imaging Spectrometer (EIS) on board Hinode Asai et al. (28); Harra et al. (211). Then, we come to an issue what EIT waves are. Eto et al. (22) clearly showed that an EIT wave is different from an Hα Moreton wave, based on simultaneous observations of them. On the other hand, Warmuth et al. (24a,b) argue that the velocity discrepancy of EIT and Moreton waves can be explained by the deceleration of coronal waves. The mechanism of EIT waves remains, therefore, very controversial (Warmuth 27; Wills-Davey & Attrill 29; Gallagher & Long 21). Delannée & Aulanier (1999); Chen et al. (22, 25) proposed the field-line stretching model for EIT waves. They suggested that EIT bright fronts were not waves at all, but instead plasma compression at stable flux boundaries due to rapid magnetic field expansion. This model can also resolve the discrepancy that EIT waves often stop at magnetic separatrices, which arises if EIT waves are the fast mode MHD waves. recent observation of fast EUV coronal waves by SDO/AIA? Chen & Wu (211) recently found coexisting EIT wave and fast coronal wave from EUV observations taken by SDO/AIA. Although the fast coronal wave seems to be the coronal

3 3 counterpart of a Moreton wave, they used only EUV images, and it remained to be confirmed whether it is a classical Hα Moreton wave. ( ) This letter presents the first simultaneous observation of EIT waves and Moreton wave by using EUV and Hα images. Moreover, we found not only a winking filament on the disk, but also, for the first time, an oscillating prominence on the limb, triggered by coronal wave (Moreton wave). 2. Observations An intense flare, X6.9 on the GOES scale, occurred on 211 August 9 at the Active Region NOAA (N14, W69 ). The flare was very impulsive, and started at 7:48 UT and peaked at 8:5 UT. Associated with the flare, we observed Moreton wave in the Hα images obtained by the Solar Magnetic Activity Research Telescope (SMART; UeNo et al. 24), at Hida Observatory, Kyoto University, Japan. SMART regularly observes the fulldisk sun in seven wavelengths around the Hα line ( Å), i.e., Hα center and the wings at ±.5 Å, ±.8 Å, and ±1.2 Å. The time cadence is 2 minutes for each wavelength during the impulsive phase of the flare, and the pixel size is.56. The Hα Moreton wave associated with the flare was very transient, and was seen only from 8:2 UT to 8:8 UT with the SMART data. Figure 1 shows the Hα Moreton wave taken by SMART. It mainly traveled south-east direction from the flare site. The propagating speed was about 76 km s 1. EUV telescopes on board satellites also observed the flare and associated wave phenomena. To compare the physical features of Moreton waves with wave-like phenomena observed in EUVs, we used EUV images taken by the Atomospheric Imaging Assembly (AIA; reference?) on board the Solar Dynamic Observatory (SDO; reference?). In this letter we mainly used the 193 Å images, which mainly contain the Fe xii (log(t) 6.1) line. The temporal resolution of the AIA 193 Å data during the flare was 12 second. The flare site was close to the west limb. We also used the EUV images taken with the Extreme-Ultraviolet Imager (EUVI) of the Sun Earth Connection Corona and Heliospheric Investigation (SECCHI; Howard et al. 28) on board the Solar Terrestrial Relations Observatory (STEREO; Kaiser et al. 28)-Ahead satellite. The STEREO-Ahead satellite was 1.7 ahead of the earth at the flare. The temporal resolutions of the 195 Å and 34 Å data, which we used in this letter, were 5 and 1 minutes, respectively. The pixel size of the images is Figure 2 shows the wave propagation seen in the SDO/AIA 193 Å images (top) and in the STEREO-A/SECCHI/EUVI 195 Å images (bottom). All are difference images, and are subtracted by the intensity maps taken at 7:55:19 UT for SDO/AIA 193 Å data, and at 7:55:31 UT for STEREO-A/SECCHI/EUVI data, respectively. The right panels of

4 4 Figure 2 show the magnetic potential field lines for the view from the earth (top) and from the STEREO-A satellite (bottom), respectively. In the images at 8:5 UT, we can identify sharp wave fronts traveling southward from the flare site, while the sharp fronts disappear after 8:1 UT. These transient and sharp wave fronts are similar to the one reported by Thompson et al. (2). The EIT wave was blocked by small ARs in traveling, and did not show the typical isotropic feature. On the other hand, the magnetic field of the southern region of the AR NOAA 11263, where the EUV wave dominantly propagates, is weak. The part of the EIT wave traveling southward, which is shown with the arrows in Figure 2, traveled with the velocity of about 7 km s 1 without being disturbed by such ARs. The wave front is much fainter than that at 8:5 UT. 3. Analysis and Results In Figure 3(a) and (b) we showed the comparison of the spatial structure of the Hα Moreton wave with that of the EUV wave of this flare. Figure 3(a) and (b) are the difference images in AIA 193 Å and in SMART Hα center, respectively. The time difference is noted in the Figure. The plus (+) signs follow the front of the Hα Moreton wave. The Moreton wave front is well coincident with the sharp EUV wave front. In addition, we can identify an expanding dome on the wave front in AIA EUV images. Therefore, the expanding dome is thought to be a shock front traveling in the corona, and the Moreton wave and the sharp EUV wave are the intersect with the chromosphere. We examined the temporal features of the EUV wave, by using the time-distance diagrams (time-slice images) along the lines shown in the Figure 3(a). Figure 3(c), (d), and (e) are the time-slice images for the Line 1, 2, and 3, respectively. For each diagram, the flare site was set to be zero. The Line 1 mainly follows the dome structure expanding in the corona, and is drawn with a straight line. In the time-slice images (Figure 3c) we can see faint bright pass (F1) with the traveling velocity of about 76 km s 1. Behind the bright front, we can also identify the dimming feature. The Line 2 mainly follows the same pass of the Hα Moreton wave, and is drawn along a great circle of the solar surface from the flare site. The front is very bright and sharp from 8:1 to 8:9 UT (F2b), which is almost the same time range of Moreton wave. Even after 8:9 UT, we can identify the wave front, while the front became much fainter (F2f). The traveling velocities are about 73 km s 1 and 62 km s 1 for F2b and F2f, respectively. Along the Line 3, we cannot clearly see the fast features such as the Moreton wave front or fast EUV wave, but bright EUV wave-like feature like a typical EIT wave (Sb). The Line 3 also follows a great circle of the solar surface from the flare site. The traveling velocity of the bright front is initially about 55 km s 1,

5 5 and slow down to be about 34 km s 1 after 8:6 UT. The bright and slow EUV wave suddenly disappears at about 8:12 UT. On the other hand, we can identify faint and fast feature (F3f) along the Line 3 from 8:6 UT. The velocity is about 58 km s 1. F3f seems to be the fast mode MHD wave, and propagates ahead of the EIT wave (Chen & Wu 211). As we mentioned above, the EUV wave is blocked by small ARs surrounding the AR NOAA These small closed loops start to oscillate due to the propagation of the coronal wave. Along the Line 2 and 3, we can identify some oscillating features. Associated with the flare, we also observed the oscillations of a prominence on the west limb and a filament on the disk. It is the first time to observe the oscillations of a prominence and a filament simultaneously, associated with a flare. The sites of the prominence/filament oscillations are shown in the Figure 1, with the characters P (prominence) and F (filament), respectively. In Figure 4 we show the temporal evolution of the limb prominence (P) in Hα images taken by SMART and in the EUV (193 Å) images taken by AIA. As the SMART wing data clearly show, the prominence moves not only in the north-south direction, i.e. the movement in the plane, but also in the line of the sight. First, the prominence became bright in the plus wing. More precisely, the initial sign of the oscillation is identified with the darkening of the prominence in the.5 Å image taken at 8:11:57 UT. In the sequence of 8:14 UT, (at least, a part of) the prominence is the brightest even in the most redward wing image of the observation, i.e Å image (8:14:24 UT). This means that the prominence is moving away with Doppler velocity of about 5 km s 1 or even faster. After this, the motion of the prominence turned to be blueward (approaching), and in the sequence of 8:22 UT, it is brightest in the 1.2 Å images (8:21:45 UT). The oscillating period is roughly about 15 minutes. In the AIA EUV images, we can clearly see the motion in the plane. Initially it moves southward (downward), then moves upward after 8:17 UT. The oscillating period is about minutes, and the amplitude is about 1, km. In the top panels of Figure 5 we show the time-slice images of the oscillating prominence in Hα center (top) and in EUV (193 Å) (bottom). The slit positions are shown in Figure 4. The oscillation of the limb prominence is identified as a filament oscillation in the EUVI 34 Å images, and we used the images to determine the precise distance from the flare site. From the start time of the oscillation and the site of the prominence, the coronal wave propagating with the velocity of about 8 km s 1 is expected to activate the prominence. A filament on the disk F, which is marked in the Figure 1, also showed oscillating features, even the features are much weaker both in the line-of-the-sight direction and in

6 6 the plane than those for the limb prominence P. The start of the oscillation is roughly estimated as 8:17:57 UT from the Hα wing images. The oscillating period is about 15 minutes. We have to note that we can identify small activation at the footpoints of the filament F at 8:1:31, which is almost the same time as the flare started. Therefore, some weak movements of the filament already started when the coronal disturbance arrived at the filament. From the start time of the oscillation and the site of the filament, we expect the coronal wave propagating with the velocity of about 57 km s Summary and Conclusions In this letter we simultaneously observed, for the first time, the Hα Moreton wave and corresponding fast EUV wave. We also observed the slow EUV wave (typical EIT wave). The Moreton wave front was well consistent with the fast-bright-sharp EUV wave front (F2b). Even after the Moreton wave disappeared, we identified the propagation of the fastfaint EUV wave (F2f). These fast EUV waves (F1, F2b, F2f, F3) are thought to be the fast mode MHD waves. Especially, when the shock strongly contacts with the chromosphere, the intersection is observed as the Moreton wave (F2b). EUV wave EUV wave (Moreton wave) (Line 3). EUV wave (EIT wave) AR EUV wave prominence oscillation must be triggered by the invisible Moreton wave fast EUV wave for this flare. We also found, for the first time, simultaneously an oscillating prominence and filament. To trigger the oscillation, the coronal wave should be as fast as the fast mode MHD wave with the velocity of about 57 8 km s 1. Therefore, both of the prominence and the filament were activated by the fast mode coronal wave in the current case. Figure 5: height-time diagram In the metric radio spectrogram (25 25 MHz) observed with the Hiraiso Radio Spectrograph (HiRAS; Kondo et al. 1995), we identify the type-ii radio burst from 8:2:4 to 8:6:3 UT. Assuming the coronal density model proposed by?, we derived the propagating velocity of about 85 km s 1. The coronal mass ejection (CME) associated with the flare was observed by the Large Angle and Spectrometric Coronagraph (LASCO; Brueckner et al. 1995) telescopes C2 and

7 7 C3 on board the SOHO. We followed the front of the CME. The temporal evolution of the CME front is shown in the Figure 5(c). By fitting them with a linear function, we derived the velocity to be about 118 km s 1. We are grateful to *** Facilities: SDO/AIA, SMART, STEREO/SECCHI/EUVI. REFERENCES Asai, A., Hara, H., Watanabe, T., Imada, S., Sakao, T., Narukage, N., Culhane, J. L., Doschek, G. A. 28, ApJ, 685, 622 Chen, P. F., Wu, S. T., Shibata, K., Fang, C. 22, ApJ, 572, L99 Chen, P. F., Fang, C., Shibata, K. 25, ApJ, 622, 122 Chen, P. F., Wu, Y. 211, ApJ, 732, L2 Delannée & Aulanier 1999 Sol. Phys., 19, 17 Eto, S., et al. 22, PASJ, 54, 481 Gallagher, P. T. & Long, D. M. 21, Space Sci. Rev., 158, 365 Harra, L. K., Sterling, A. C., Gömöry, P., Veronig, A. 211, ApJ, 737, L4 Kai, K. 197, Sol. Phys., 11, 31 Kaiser, M. L., Kucera, T. A., Davila, J. M., St. Cyr, O. C., Guhathakurta, M., Christian, E. 28, Space Sci. Rev., 163, 5 Khan, J. I. & Aurass, H. 22, A&A, 383, 118 Khan, J. I. & Hudson, H. S. 2, Geophys. Res. Lett., 27, 183 Klassen, A., Aurass, H., Mann, G., Thompson, B. J. 2, A&AS, 141, 357 Moreton, G. E. 196, AJ, 65, 494 Narukage, N., Hudson, H. S., Morimoto, T., Akiyama, S., Kitai, R., Kurokawa, H., Shibata, K. 22, ApJ, 572, L19

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9 9 Fig. 1. Moreton wave observed with SMART.

10 SDO/AIA 193A 1 8:1:43 8:15:31 STEREO-A/EUVI 195A 8:5:31 P 8:5:31 8:1:31 8:15:31 Fig. 2. EUV waves observed with SDO/AIA 193 AA (top) and STEREOA/SECCHI/EUVI 195 A (bototm). The arrows follow the front of the wave. The region with mark P points the position of the limb prominence. The right panels show the magnetic potential field lines for the views from the earth (top) and from the STEREO-A (bottom).

11 distance [15km] 11 5 (c) 4 Line 1 F1 8 4 km/s Line 3 (d) Line 2 F2f Line 2 Line 1 (a) AIA 193 8:6:19-8::19 distance [15km] 4 F2b (e) Line 3 distance [15km] 4 F3 Sb (b) SMART Hαcenter 8:6:3-8:4:3 8:4 8:8 8:12 8:16 Time (9-Aug-211) 8:2 Fig. 3. Detailed feature of coronal disturbances. (a) Difference image (8:6:19 8::19 UT) of EUV 193 A image taken by SDO/AIA, and (b) difference image (8:6:3 8:4:3 UT) of Hα center image taken by SMART. The plus (+) signs follow the Moreton wave front. (c e) Time-distance diagrams (time-slice images) of AIA EUV 193 A image along the line 1, 2, and 3, respectively. The line is also shown in (a). The white arrows point the oscillating features caused during the propagation of the EUV waves.

12 12 8:1 8:12 8:14 8:16 8:18 SMART +.5A center -.5A 1" S N N AIA 193A S Fig. 4. Temporal evolution of the oscillating prominence. From top to bottom: Hα.5 Å, center images, and +.5 Å images taken by SMART, EUV 193 Å images taken by SDO/AIA. The field of view of the panes is the same as the region P shown in Figure 1.

13 13 distance [arcsec] distance [arcsec] distance [1 6 km] (a) AIA 193A SMART Ha center N S (b) Line1 (F1) Line2 (F2) Line3 (F3f) Line3 (Sb) P prominence F filament Type-II burst (c) LASCO C3 LASCO C2 P 8 4 km/s 8: 8:1 8:2 8:3 8: 9: 1: 11: Time (9-Aug-211) [UT] F 12 km/s 6 distance [1 4 km] distance [1 5 km] distance [R sun ] Fig. 5. Height-time plot of the flare-related phenoma. ( ). Type-II burst (r=r sun ). AIA Figure 3. Line1 Line2/3 ( ).