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Using data obtained with the 20-cm H full-disk telescope at Big Bear Solar Observatory and Fexii 195 Å EIT on SOHO, we analyze a sudden disappearance event of a quiescent filament in detail. The filament was located along the common boundary of the active regions NOAA 9672 (S19 E13) and NOAA 9673 (N03 E18). The filament disappeared during a time interval between 17:59 UT and 19:47 UT on 22 October 2001 immediately after the onset of a major flare, which occurred in the active region NOAA 9672. At about 23:23 UT of the same day, the filament began to reappear in H and, after about 15 hours, the filament recovered to its steady state with its size being slightly smaller than that before its disappearance. This filament disappearance event belongs to the thermal type of sudden filament disappearances, which is caused by an input of additional heat. The heating mechanism that leads to sudden thermal disappearances of quiescent filaments is still not well understood. This simple event, due to the explicit cause and effect relationship between the flare and the disappearance of the filament, shows us that the flare triggered some kind of heating mechanism which continued several hours. The heat may come from the flare via heat conduction from its ribbon or from the excitation of dissipating Alfvén waves. However, from the data analysis, we conclude that the flare triggered an in-situ heating, which is likely caused by magnetic reconnection. 相似文献
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H. Wang C. Denker T. Spirock P.R. Goode S. Yang W. Marquette J. Varsik R.J. Fear J. Nenow D.D. Dingley 《Solar physics》1998,183(1):1-13
A new digital magnetograph system has been installed and tested at Big Bear Solar Observatory. The system uses part of BBSO's existing videomagnetograph (VMG) system: a quarter wave plate, a ferro-electric liquid crystal to switch polarizations, and a 0.25 Å bandpass Zeiss filter tuned at Cai 6103 Å. A new 256×256 pixels, 12-bit Dalsa camera is used as the detector and as the driver to switch the liquid crystal. The data rate of the camera is 90 frames s–1. The camera is interfaced to a Pentium-166 PC with a Tech imaging board for data acquisition and analysis. The computer has 128 MByte of RAM, and up to 700 live images can be stored in memory for quick post-exposure image processing (image selection and alignment). We have significantly improved the sensitivity and spatial resolution over the old BBSO VMG system. In particular: (1) New digital image data are in 12 bits while the video signal is digitized as 8 bits. Polarizations weaker than 1% can not be detected by a single pair subtraction in the video system. The digital system can detect a polarization signal of about 0.3% by a single pair subtraction. (2) Data rate of the digital system is 90 frames s–1, that of the video system is 30 frames s–1. So the time difference between two polarizations is reduced in the new system. Under good seeing conditions, the data rate of 90 frames s–1 ensures that most of the wavefront distortions are frozen and fairly closely the same for the left and right circular polarized image pairs. (3) Magnetograms are constructed after image selection and alignment. We discuss the characteristics of this new system. We present the results of our first tests to reconstruct magnetograms with speckle interferometric techniques. We also present some preliminary results on the comparison of facular/micropore contrasts and magnetic field structure. The experiment with this small detector lays ground for a larger format digital magnetograph system at BBSO, as well as a future Fabry-Pérot system, which will be able to scan across the spectral line. 相似文献
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Chae Jongchul Denker Carsten Spirock Tom J. Wang Haimin Goode Philip R. 《Solar physics》2000,195(2):333-346
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. 相似文献
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We present observations of four filaments that exhibit large-amplitude periodic mass motion. Observations are obtained using
the high resolution (2″) and high cadence (1 min) Hα telescope system at the Big Bear Solar Observatory (BBSO). The motions
found in these events are along the axis of the filaments, and are associated with the activity of a nearby flare or filament.
The most characteristic properties of these motions are long period (≥ q80 min), large distance (≥ q 4 × 104 km) of mass transport at much higher velocity (≥ q 30 km s−1) than ever detected from filament motions. The velocity, period, dimension and damping timescale measured for these motions
are presented, and discussed to identify the most plausible restoring force and damping mechanism. 相似文献
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We present a new method to resolve the 180° ambiguity for solar vector magnetogram measurements. The basic assumption is that the magnetic shear angle (), which is defined as the difference between the azimuth components of observed and potential fields, approximately follows a normal distribution. The new method is composed of three steps. First, we apply the potential field method to determine the azimuthal components of the observed magnetic fields. Second, we resolve the ambiguity with a new criterion: –90°+mp
lele90°+mp, where mp is the most probable value of magnetic shear angle from its number distribution. Finally, to remove some localized field discontinuities, we use the criterion B
tB
mt
ge0, where B
t and B
mt are an observed transverse field and its mean value for a small surrounding region, respectively. For an illustration, we have applied the new ambiguity removal method (Uniform Shear Method) to a vector magnetogram which covers a highly sheared region near the polarity inversion line of NOAA AR 0039. As a result, we have found that the new ambiguity solution was successful and removed spatial discontinuities in the transverse vector fields produced in the magnetogram by the potential field method. It is also found that our solution to the ambiguity gives nearly the same results, for highly sheared vector magnetograms and vertical current density distributions, of NOAA AR 5747 and AR 6233 as those of other methods. The validity of the basic assumption for an approximate normal distribution is demonstrated by the number distributions of magnetic shear angle for the three active regions under consideration. 相似文献
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Wenda Cao Klaus Hartkorn Jun Ma Yan Xu Tom Spirock Haimin Wang Philip R. Goode 《Solar physics》2006,238(1):207-217
We discuss a near-infrared (NIR) narrow-band tunable birefringent filter system newly developed by the Big Bear Solar Observatory (BBSO). This is one of the first narrow-bandpass NIR filter systems working at 1.56 μm which is used for the observation of the deepest solar photosphere. Four stages of calcite were used to obtain a bandpass of 2.5 Å along with a free spectral range (FSR) of 40 Å. Some unique techniques were implemented in the design, including liquid crystal variable retarders (LCVRs) to tune the bandpass in a range of ±100 Å, a wide field configuration to provide up to 2° incident angle, and oil-free structure to make it more compact and handy. After performing calibration and characteristic evaluation at the Evans Facility of the National Solar Observatory at Sacramento Peak (NSO/SP), a series of high-resolution filtergrams and imaging polarimetry observations were carried out with the Dunn Solar Telescope of NSO/SP and the 65-cm telescope of BBSO, in conjunction with the high-order adaptive optics system and the Fabry–Pérot Interferometer (FPI). In this paper, we describe the optical design and discuss the calibration method. Preliminary observations show that it is capable of serving as either a stand-alone narrow-band filter for NIR filtergram observations or an order-sorting filter of a FPI applied to NIR two-dimensional imaging spectro-polarimetry. 相似文献
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Yan Xu Guo Yang Jiong Qiu Tom J. Spirock Ju Jing Carsten Denker Haimin WangCenter for Solar-Terrestrial Research New Jersey Institute of Technology Martin Luther King Blvd Newark NJ USA 《中国天文和天体物理学报》2004,4(5):481-489
We compare the contrast of faculae, in visible light and in the near infrared (NIR), that were associated with the active region NOAA 8518 which crossed the solar disk from April 19 to 27, 1999. We obtained NIR continuum images at 1.6 μm at the Big Bear Solar Observatory (BBSO) with an Indium Gallium Arsenide (In Ga As) NIR digital camera. We also obtained high-resolution longitudinal magnetograms and visible light filtergrams at 610.3 nm with the newly developed Digital Vector Magnetograph (DVMG). Our data show that the contrast of faculae has the same sign in both the visible and the NIR. We did not find any so-called “dark faculae”, faculae that are bright in the visible and simultaneously dark in the NIR.We determined a threshold magnetic flux density that separates pores from faculae. 相似文献
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