115149137
CONTRACTING AND ERUPTING COMPONENTS OF SIGMOIDAL ACTIVE REGIONS
It has recently been noted that solar eruptions can be associated with the contraction of coronal loops that are not involved in magnetic reconnection processes. In this paper, we investigate five coronal eruptions originating from four sigmoidal active regions, using high-cadence, high-resolution narrowband EUV images obtained by the Solar Dynamic Observatory (SDO). The magnitudes of the flares associated with the eruptions range from GOES class B to class X. Owing to the high-sensitivity and broad temperature coverage of the Atmospheric Imaging Assembly (AIA) on board SDO, we are able to identify both the contracting and erupting components of the eruptions: the former is observed in cold AIA channels as the contracting coronal loops overlying the elbows of the sigmoid, and the latter is preferentially observed in warm/hot AIA channels as an expanding bubble originating from the center of the sigmoid. The initiation of eruption always precedes the contraction, and in the energetically mild events (B- and C-flares), it also precedes the increase in GOES soft X-ray fluxes. In the more energetic events, the eruption is simultaneous with the impulsive phase of the nonthermal hard X-ray emission. These observations confirm that loop contraction is an integrated process in eruptions with partially opened arcades. The consequence of contraction is a new equilibrium with reduced magnetic energy, as the contracting loops never regain their original positions. The contracting process is a direct consequence of flare energy release, as evidenced by the strong correlation of the maximal contracting speed, and strong anti-correlation of the time delay of contraction relative to expansion, with the peak soft X-ray flux. This is also implied by the relationship between contraction and expansion, i.e., their timing and speed.
41231566
Quantitative Analysis of CME Deflections in the Corona
In this paper, ten CME events viewed by the STEREO twin spacecraft are analyzed to study the deflections of CMEs during their propagation in the corona. Based on the three-dimensional information of the CMEs derived by the graduated cylindrical shell (GCS) model (Thernisien, Howard, and Vourlidas in Astrophys. J.652, 1305, 2006), it is found that the propagation directions of eight CMEs had changed. By applying the theoretical method proposed by Shen et al. (Solar Phys.269, 389, 2011) to all the CMEs, we found that the deflections are consistent, in strength and direction, with the gradient of the magnetic energy density. There is a positive correlation between the deflection rate and the strength of the magnetic energy density gradient and a weak anti-correlation between the deflection rate and the CME speed. Our results suggest that the deflections of CMEs are mainly controlled by the background magnetic field and can be quantitatively described by the magnetic energy density gradient (MEDG) model.
55112542
Statistical Study of Coronal Mass Ejection Source Locations: II. Role of Active Regions in CME Production
This is the second paper of the statistical study of coronal mass ejection (CME) source locations, in which the relationship between CMEs and active regions (ARs) is statistically studied on the basis of the information of CME source locations and the ARs automatically extracted from magnetic synoptic charts of Michelson Doppler Imager (MDI) during 1997 -- 1998. It is found that about 63% of the CMEs are related with ARs, at least about 53% of the ARs produced one or more CMEs, and particularly about 14% of ARs are CME-rich (3 or more CMEs were generated) during one transit across the visible disk. Several issues are then tried to clarify: whether or not the CMEs originating from ARs are distinct from others, whether or not the CME kinematics depend on AR properties, and whether or not the CME productivity depends on AR properties. The statistical results suggest that (1) there is no evident difference between AR-related and non-AR-related CMEs in terms of CME speed, acceleration and width, (2) the size, strength and complexity of ARs do little with the kinematic properties of CMEs, but have significant effects on the CME productivity, and (3) the sunspots in all the most productive ARs at least belong to $\beta\gamma$ type, whereas 90% of those in CME-less ARs are $\alpha$ or $\beta$ type only. A detailed analysis on CME-rich ARs further reveals that (1) the distribution of the waiting time of same-AR CMEs, consists of two parts with a separation at about 15 hours, which implies that the CMEs with a waiting time shorter than 15 hours are probably truly physical related, and (2) an AR tends to produce such related same-AR CMEs at a pace of 8 hours, but cannot produce two or more fast CMEs (>800 km/s) within a time interval of 15 hours. This interesting phenomenon is particularly discussed.
118595496
SOLAR LIMB PROMINENCE CATCHER AND TRACKER (SLIPCAT): AN AUTOMATED SYSTEM AND ITS PRELIMINARY STATISTICAL RESULTS
In this paper, we present an automated system, which has the capability to catch and track solar limb prominences based on observations from the extreme-ultraviolet (EUV) 304?? passband. The characteristic parameters and their evolution, including height, position angle, area, length, and brightness, are obtained without manual interventions. By applying the system to the STEREO-B/SECCHI/EUVI 304?? data during 2007 April-2009 October, we obtain a total of 9477 well-tracked prominences and a catalog of these events available online. A detailed analysis of these prominences suggests that the system has a rather good performance. We have obtained several interesting statistical results based on the catalog. Most prominences appear below the latitude of 60? and at the height of about 26 Mm above the solar surface. Most of them are quite stable during the period they are tracked. Nevertheless, some prominences have an upward speed of more than 100 km s?1, and some others show significant downward and/or azimuthal speeds. There are strong correlations among the brightness, area, and height. The expansion of a prominence is probably one major cause of its fading during the rising or erupting process.
55072733
Source Region of the Decameter–Hectometric Type II Radio Burst: Shock–Streamer Interaction Region
D–H type II radio bursts are widely thought to be caused by coronal mass ejections (CMEs). However, it is still unclear where the exact source of the type IIs on the shock surface is. We identify the source regions of the decameter–hectometric (D–H) type IIs based on imaging observations from SOHO/LASCO and the radio dynamic spectrum from Wind/Waves. The analysis of two well-observed events suggests that the sources of these two events are located in the interaction regions between shocks and streamers, and that the shocks are enhanced significantly in these regions.
15282196
STRENGTH OF CORONAL MASS EJECTION-DRIVEN SHOCKS NEAR THE SUN AND THEIR IMPORTANCE IN PREDICTING SOLAR ENERGETIC PARTICLE EVENTS
Coronal shocks are important structures, but there are no direct observations of them in solar and space physics. The strength of shocks plays a key role in shock-related phenomena, such as radio bursts and solar energetic particle (SEP) generation. This paper presents an improved method of calculating Alfven speed and shock strength near the Sun.This method is based on using as many observations as possible, rather than one-dimensional global models. Two events, a relatively slow CME on 2001 September 15 and a very fast CME on 2000 June 15, are selected to illustrate the cal- culation process. The calculation results suggest that the slow CME drove a strong shock, with Mach number of 3.43- 4.18, while the fast CME drove a relatively weak shock, with Mach number of 1.90-3.21. This is consistent with the radio observations, which find a stronger and longer decameter-hectometric (DH) type II radio burst during the first event, and a short DH type II radio burst during the second event. In particular, the calculation results explain the observational fact that the slow CME produced a major solar energetic particle (SEP) event, while the fast CME did not. Through a comparison of the two events, the importance of shock strength in predicting SEP events is addressed. Subject headingg acceleration of particles — shock waves — Sun: coronal mass ejections (CMEs)
119260012
Multiwavelength properties of a new Geminga-like pulsar: PSR J2021+4026
In this paper, we report on a detailed investigation of the multiwavelength properties of a newly detected gamma-ray pulsar, PSR J2021+4026, in both observational and theoretical aspects. We first identify an X-ray source in the XMM-Newton serendipitous source catalogue, 2XMM J202131.0+402645, located within the 95 per cent confidence circle of PSR J2021+4026. With an archival Chandra observation, this identification provides an X-ray position with arcsecond accuracy which is helpful in facilitating further investigations. Searching for the pulsed radio emission at the position of 2XMM J202131.0+402645 with a 25-m telescope at Urumqi Astronomical Observatory resulted in null detection and places an upper limit of 0.1 mJy for any pulsed signal at 18 cm. Together with the emission properties in X-ray and gamma-ray, the radio quietness suggests PSR J2021+4026 to be another member of Geminga-like pulsars. In the radio sky survey data, extended emission features have been identified in the gamma-ray error circle of PSR J2021+4026. We have also re-analysed the gamma-ray data collected by Fermi's Large Area Telescope. We found that the X-ray position of 2XMM J202131.0+402645 is consistent with that of the optimal gamma-ray timing solution. We have further modelled the results in the context of the outer gap model, which provides us with constraints for the pulsar emission geometry such as the magnetic inclination angle and the viewing angle. We have also discussed the possibility of whether PSR J2021+4026 has any physical association with the supernova remnant G78.2+2.1 (gamma-Cygni).
119188008
Single spin asymmetries in charged kaon production from semi-inclusive deep inelastic scattering on a transversely polarized He 3 target
We report the first measurement of target single spin asymmetries of charged kaons produced in semi-inclusive deep inelastic scattering of electrons off a transversely polarized He^3 target. Both the Collins and Sivers moments, which are related to the nucleon transversity and Sivers distributions, respectively, are extracted over the kinematic range of 0.1<x_(bj) <0.4 for K+ and K− production. While the Collins and Sivers moments for K+ are consistent with zero within the experimental uncertainties, both moments for K− favor negative values. The Sivers moments are compared to the theoretical prediction from a phenomenological fit to the world data. While the K+ Sivers moments are consistent with the prediction, the K− results differ from the prediction at the 2-sigma level.
122216623
Measuring accelerating universe with high-redshift GRBs data and other cosmological probes
A kinematical model (a parameterized deceleration parameter) and a dynamical model (a parameterized equation of state for dark energy) are constrained from the current observational data including the high-redshift Gamma-Ray Bursts (GRBs) data with a redshift range from 1.4 to 9. We obtain the stringent constraint on the values of current deceleration parameter q0, current jerk parameter j0, current equation of state for dark energy w0de and transition redshift zT. In addition, we compare the difference of the constraint results between the kinematical and the dynamical scenarios.
124567745
Observation of the 2005 January 20 GLE event using Yangbajing. solar neutron telescope & neutron monitor
A solar cosmic rays Ground Level Enhancement (GLE) event associated with a X7.1/2b solar flare in 2005 January 20 was observed by the Yangbajing solar neutron telescope(SNT) and neutron monitor(NM), located at Yangbajing Tibet(90.53 degrees E, 30.11 degrees N, 4310m a.s.l) with the highest vertical geomagnetic cut-off rigidity of 14.1GV in NM network. The statistical significance of the counting rate enhancement recorded by solar neutron telescope in > 40MeV channel was 3.7 sigma in the time window of 07:00-07:05UT and 6.0 sigma in the time window of 07:00-07:20UT, respectively. The onset time of 06:51-06:52UT for this GLE event was clearly observed by the Yangbajing NM. Our observation indicates that solar protons have been accelerated up to energies of > 10GeV during this solar event.
115467667
KamLAND: A Liquid scintillator anti-neutrino detector at the Kamioka site
We present the initial design of a very large kton liquid scintillator detector to be installed in the underground cavity where Kamiokande used to be The ex periment is optimized to detect low energy anti neutrinos and it will perform unique measurements in the elds of neutrino physics geophysics and astrophysics One of the initial goals will be to perform a very long baseline oscillation experiment using a large number of nuclear reactors Such an experiment will be sensitive to neutrino masses as low as m eV attacking for the rst time with a laboratory measurement some of the possible solutions to the solar neutrino anomaly This can be considered the ultimate neutrino mass test using the oscillation technique The observation of neutrinos from the Earth supernovae atmosphere and nucleon decay will also be part of a very rich initial program while in a later stage the ob servation of solar neutrinos and other channels requiring ultra low background will become the main focus KamLAND is conceived as a scalable detector that will be able to start in a very short time to deliver results on a number of essential physics issues that only require present day technology This rst running period will also establish backgrounds and detector requirements for a second ultra low background running phase