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1.
We investigate the emergence of Active Region NOAA 10790 by means of time?–?distance helioseismology. Shallow regions of increased sound speed at the location of increased magnetic activity are observed, with regions becoming deeper at the locations of sunspot pores. We also see a long-lasting region of decreased sound speed located underneath the region of the flux emergence, possibly relating to a temperature perturbation due to magnetic quenching of eddy diffusivity, or to a dense flux tube. We detect and track an object in the subsurface layers of the Sun characterised by increased sound speed which could be related to emerging magnetic-flux and thus obtain a provisional estimate of the speed of emergence of around 1 km?s?1.  相似文献   

2.
The motion of dust structures in the circumnuclear region of comet Hale–Bopp is studied. About 270 envelope images were obtained with the AZT-8 reflector (D = 0.7 m, F = 28 m) and the Filin-3 image intensifier. We carried out our observations at the observational station of the Astronomical Observatory of Shevchenko Kiev State University in the village of Lesniki (near Kiev). The recording from the image-intensifier screen was made on Foto-100 film during 23 nights from March 24 to May 10, 1997. The circumnuclear region was imaged both in white light (without filters) and with IHW CO+ (ef = 426 nm), C3 (ef = 496 nm), C2 (ef = 514 nm), and RC (red continuum, ef = 684 nm) narrow-band interference filters. Based on our measurements of the radial expansion of dust structures, we determined the velocities, 0.61–1.99 km s–1; accelerations, from –18.3 × 10–3 to 4.0 × 10–3 m s–2; and rotation period of the cometary nucleus, 111.41h ± 0.05h.  相似文献   

3.
The frequency intervals in which O VI ions get in resonance with ion–cyclotron waves are calculated using the kinetic model, for the latest six values found in literature on O VI ion number densities in the 1.5R–3R region of the NPCH. It is found that the common resonance interval is 1.5 kHz to 3 kHz. The R-variations of wave numbers necessary for the above calculations are evaluated numerically, solving the cubic dispersion relation with the dielectric response derived from the quasi-linear Vlasov equation for the left-circularly polarized ion-cyclotron waves.  相似文献   

4.
We study the dynamic evolution of the time series describing the plage regions areas observed daily at the Observatório Astronómico da Universidade de Coimbra, in each one of the solar hemispheres during solar cycles 21?–?23. The classical ARMA model has proven to be insufficient to describe the time variations seen in the data because of the strong conditional variability. We found that the data are well fitted by ARMA mixed with power-δ TGARCH error models. The power index δ is non-integer; this property has recently been introduced in the literature on time-series analyses and indicates the presence of strong volatility and long memory in the data series. We also detected dynamic asymmetry in the plage region areas observed in the two hemispheres when two different temporal models were obtained to fit them. The finding of a dynamic asymmetry is also supported by the dynamic evolution of the daily difference (north–south) time series, which is significantly different from white noise. This statistical modeling of time series, taking into account new and different characteristics of the solar activity, will be very useful in subsequent forecast developments.  相似文献   

5.
Outflows of plasma at the edges of active regions surrounded by quiet Sun are now a common observation with the Hinode satellite. While there is observational evidence to suggest that the outflows are originating in the magnetic field surrounding the active regions, there is no conclusive evidence that reveals how they are driven. Motivated by observations of outflows at the periphery of a mature active region embedded in a coronal hole, we have used a three-dimensional simulation to emulate the active region’s development in order to investigate the origin and driver of these outflows. We find that outflows are accelerated from a site in the coronal hole magnetic field immediately surrounding the active region and are channelled along the coronal hole field as they rise through the atmosphere. The plasma is accelerated simply as a result of the active region expanding horizontally as it develops. Many of the characteristics of the outflows generated in the simulation are consistent with those of observed outflows: velocities up to 45 km s−1, properties akin to the coronal hole, proximity to the active region’s draining loops, expansion with height, and projection over monopolar photospheric magnetic concentrations. Although the horizontal expansion occurs as a consequence of the active region’s development in the simulation, expansion is also a general feature of established active regions. Hence, it is entirely possible and plausible that the expansion acceleration mechanism displayed in the simulation is occurring in active regions on the Sun and, in addition to reconnection, is driving the outflows observed at their edges.  相似文献   

6.
Over the bipolar sunspot in the active region,a qualitative model of quasi-open magnetic field line region Is proposed to explain the relationship betweenthe energetic electron beams in the corona and the rapid processes in solarflares.The quasi-open field line region is established between the bottom ofthe open field line and the top of the flaring loop as shown in Fig.1.  相似文献   

7.
We present high angular resolution images of both NH3(1,1)and (2,2) lines toward NGC 7538 IRS 1.The density and velocity-position plots have been used to study the interaction among the outflows,winds and their environment.For the first time we have found an expanding half-shell of molecular gas around the HⅡ region associated with IRS 1,which may be produced by the interaction of the bipolar outflows and the winds originating in IRS 1-3,and optical HⅡ region NGC 7538 with ambient molecular gas.  相似文献   

8.
1　ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｔｈｅｍｏｒｅｔｈａｎ 5 0ｙｅａｒｓｆｒｏｍｔｈａｔｔｈｅｓｏｌａｒｒａｄｉｏａｓｔｒｏｎｏｍｙｗａｓｂｏｒｎ ,ｐｅｏｐｌｅｈａｖｅｃａｒｒｉｅｄｏｕｔａｇｒｅａｔｄｅａｌｏｆｏｂｓｅｒｖａｔｉｏｎｓａｎｄｓｔｕｄｉｅｓｏｎｒａｄｉｏｅｍｉｓｓｉｏｎｐｈｅｎｏｍｅｎａ ,ｂｕｔｉｔｗａｓｄｏｎｅｆｅｗｉｎｒａｄｉｏａｂｓｏｒｐｔｉｏｎｐｈｅｎｏｍｅｎａ .Ｉｎｆａｃｔｉｎｔｈｅｓｏｌａｒａｔｍｏｓｐｈｅｒｉｃｐｌａｓｍａ ,ｔｈｅｒａｄｉａｔｉｏｎａｎｄａｂｓｏｒｐｔｉ…  相似文献   

9.
H emission objects were searched for, using the objective-prismSchmidt plates in a 36 deg2 sky area covering the Cepheus OB3 association.Hundred and eight emission stars have been found, 68 of which are newfindings to our knowledge. The properties of the IRAS point sourcesidentified with H emission stars indicate that most of theH emission stars are T Tauri stars or related objects. Hemission stars associated with IRAS sources and those unassociated havedifferent distributions, suggesting an age sequence among them.Altogether, they show a ring- or shell-like surface distribution, whichalmost coincides with that of heated dusts, and these distributionsappear to be encompassed by an HI shell.  相似文献   

10.
An atlas of high resolution (R = 60 000) CCD-spectra in the wavelength range 3500-5000A is presented for four objects in metallicity range -3.0 < [Fe/H] < -0.6, temperature range 4750 < Teff < 5900 K, and surface gravity range 1.6 < lgg < 5.0. We describe the calibration of the stellar atmospheric parameters using Alonso's formula based on the method of infrared flux and outline the determination of the abundances of a total number of 25 chemical elements. An analysis of the abundance determination errors for different chemical elements is carried out, and a method is provided for the observations and reduction of spectral material. Properties of the method of producing an atlas of spectra and line identifications are described.  相似文献   

11.
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   

12.
Near-infrared images and K-band spectroscopy of the massive star-forming region IRAS 23151+5912 are presented. The JHK' images reveal an embed-ded infrared cluster associated with infrared nebula, and the H_2 (2.12μm) narrow-band image provides for the first time evidence of outflow activity associated withthe cluster. That the cluster is young can be shown by the high percentage ofinfrared excess sources and the outflow activity. We suggest an age of the clus-ter of ～ 10~6yr. Eight young stars are found in the bright nebular core aroundIRAS 23151+5912. By the color-magnitude diagrams of the cluster, we found fivehigh--mass YSOs and four intermediate-mass YSOs in the cluster. Eight H_2 emissionfeatures are discovered in the region with a scattered and non-axisymmetric distri-bution, indicating the existence of multiple outflows driven by the cluster. DiffuseH_2 emission detected to the north and to the west of the cluster may result fromUV leakage of the cluster. Brγ, H_2, and CIV emission lines are  相似文献   

13.
The massive star forming region S 233 IR is observed in the molecular lines CO J = 2-1, 3-2, NH3 (1,1), (2,2) and the 870#m dust continuum. Four submillimeter continuum sources, labelled SMM 1-4, are revealed in the 870μm dust emission. The main core, SMM1, is found to be associated with a deeply embedded near infrared cluster in the northeast; while the weaker source SMM2 coincides with a more evolved cluster in the southwest. The best fit spectral energy distribution of SMM1 gives an emissivity of β = 1.6, and temperatures of 32 K and 92 K for the cold- and hot-dust components. An SMM1 core mass of 246 M⊙ and a total mass of 445 M⊙ are estimated from the 870μm dust continuum emission.SMM1 is found to have a temperature gradient decreasing from inside out, indicative of the presence of interior heating sources. The total outflow gas mass as traced by the CO J = 3-2 emission is estimated to be 35 M⊙. Low velocity outflows are also found in the NH3 (1,1) emission. The non-thermal dominant NH3 line width as well as the substantial core mass suggest that the SMM1 core is a “turbulent,massive dense core”, in the process of forming a group or a cluster of stars. The much higher star formation efficiency found in the southwest cluster supports the suggestion that this cluster is more evolved than the northeast one. Large near infrared photometric variations found in the source PCS-IR93, a previously found highly polarized nebulosity, indicate an underlying star showing the FU Orionis type of behavior.  相似文献   

14.
During very intense geomagnetic storm of November 7–8, 2004 simultaneous presence of storm time disturbance dynamo and eastward and westward directed prompt penetration electric fields inferred from the ground based magnetometer data in the 75° E sector is presented. Magnetometer observations show that, on the whole, average ΔH variation on 8 November remains below the night time level compared to its quiet day variation. A number of upward and downward excursions have been observed between 0130 UT and 0800 UT in the ΔH variation on 8 November. These excursions in ΔH have been attributed to the episodes of eastward and westward prompt penetrating electric fields. Ionospheric response in the equatorial ionization anomaly region along 75° E has also been studied using the total electron content data recorded at five GPS stations, namely Udaipur, Bengaluru (IISC), Hyderabad (HYDE), Maldives (MALD) and Diego Garcia (DGAR). Observation of markedly suppressed EIA, in conjunction with ΔH variation which was m negative during the daytime on 8 November, indicates the presence of an external field of opposite polarity (the disturbance dynamo electric field) that either undermined, or overshadowed the daytime ambient (eastward) electric field to the extent that the equatorial plasma fountain could not become effective.  相似文献   

15.
Ravindra  B.  Venkatakrishnan  P. 《Solar physics》2003,215(2):239-259
The length scale and life time of the transition region network cells were studied using Heii 304 filtergrams. The temporal structure function was calculated from spatially aligned Heii 304 images. The estimated life time of the network cell was about 27 hr. We compared this life time with the life time of photospheric magnetic network and of the extrapolated magnetic network. The spatial structure function was calculated from the Heii 304 filtergrams. The calculated spatial structure function saturates at 25000 km. The transition region network elements are bigger in size than the photospheric magnetic network element. The magnetic network element equals the size of the Heii 304 network element when the photospheric magnetic field is extrapolated to a height of 3000 km above the photosphere where the magnetic fluxes are deployed. The derived value of the diffusion speed of the network elements was 0.098 km s–1.  相似文献   

16.
The sizes of the Broad Line Region (BLR) of some Seyfert 1 galax-ies and nearby quasars can be determined by the reverberation mapping method.Combining with the observed FWHM of Hβ emission line and assuming that themotion of BLR clouds is virialized, the black hole masses of these objects have beenestimated. However, this method strongly depends on the poorly-understood geom-etry and inclination of the BLR. On the other hand, a tight correlation between theblack hole mass and the bulge velocity dispersion was recently found for both activeand nearby inactive galaxies. This may provide another method, independent of theBLR geometry, for estimating the black hole mass. Using this method for estimatingthe black hole mass and combining with the measured BLR size and FWHM of Hβemission line, we derived the BLR inclination angles for 20 Seyfert I galaxies underthe assumption that the BLR is disk-like. The derived inclination angles agree wellwith those derived previously by fitting the UV continuum and Hβ emission lineprofiles. Adopting a relation between the FWHMs of [OⅢ]λ5007 forbidden line andthe stellar velocity dispersion, we also estimated the BLR inclinations for 50 nar-row line Seyfert 1 galaxies (NLSls). We found that the inclinations of broad LineSeyfert 1 galaxies (BLS1s) are systematically greater than those of NLS1s, whichseldom exceed 30. This may be an important factor that leads to the differencesbetween NLS1s and BLS1s if the BLR of NLS1s is really disk-like.  相似文献   

17.
We carried out near-infrared imaging observations of the Ori A-W region using the Italian 1.5m TIRGO infrared telescope at Gornergrat. A group of infrared objects is visible on the K band image, including an IRAS source (IRS 1). From its IRAS flux density the IRAS luminosity is derived to be 45L⊙, which shows that IRS 1 is a low-mass protostar. By superimposing the position of the VLA H2O maser on the K image, we can identify the less evolved object IRS 1 as the excitation source of the H2O maser, within a projected distance of 470AU. This would be evidence that the maser effect is associated with the youngest phase of stellar evolution. The first probable HH object candidate in the Ori A-W region is discovered from the H2 S(1) 1-0 observation. Comparing the position of the H2O maser with the direction of the molecular hydrogen emission in the region, we suggest that the observed H2O maser could be tracing the circumstellar disk of IRS 1.  相似文献   

18.
《New Astronomy Reviews》2004,48(10):843-859
If a point mass moves through a uniform gas cloud, at what rate does it accrete material? This is the question studied by Bondi, Hoyle and Lyttleton. This paper draws together the work performed in this area since the problem was first studied. Time has shown that, despite the simplifications made, Bondi, Hoyle and Lyttleton made quite accurate predictions for the accretion rate. Bondi–Hoyle–Lyttleton accretion has found application in many fields of astronomy, and these are also discussed.  相似文献   

19.
It is shown that an analog of Birkhoff’s theorem of general relativity exists in the Einstein–Cartan–Kalb–Ramond (ECKR) theory of gravity when Kalb–Ramond (KR) field strength, which occurs in the theory is independent of time.  相似文献   

20.
The geoeffective magnetic cloud (MC) of 20 November 2003 was associated with the 18 November 2003 solar active events in previous studies. In some of these, it was estimated that the magnetic helicity carried by the MC had a positive sign, as did its solar source, active region (AR) NOAA 10501. In this article we show that the large-scale magnetic field of AR 10501 has a negative helicity sign. Since coronal mass ejections (CMEs) are one of the means by which the Sun ejects magnetic helicity excess into interplanetary space, the signs of magnetic helicity in the AR and MC must agree. Therefore, this finding contradicts what is expected from magnetic helicity conservation. However, using, for the first time, correct helicity density maps to determine the spatial distribution of magnetic helicity injections, we show the existence of a localized flux of positive helicity in the southern part of AR 10501. We conclude that positive helicity was ejected from this portion of the AR leading to the observed positive helicity MC.  相似文献   

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