Conformal Symmetry and Pion Form Factor: Soft and Hard Contributions

We discuss a constraint of conformal symmetry in the analysis of the pion form factor. The usual power-law behavior of the form factor obtained in the perturbative QCD analysis can also be attained by taking negligible quark masses in the nonperturbative quark model analysis, confirming the recent AdS/CFT correspondence. We analyze the transition from soft to hard contributions in the pion form factor considering a momentum-dependent dynamical quark mass from a nonnegligible constituent quark mass at low momentum region to a negligible current quark mass at high momentum region. We find a correlation between the shape of nonperturbative quark distribution amplitude and the amount of soft and hard contributions to the pion form factor.Comment: 7 pages, 6 figures, extensively revised, to appear in Phys. Rev.

Chromospheric evaporation in sympathetic coronal bright points

{Chromospheric evaporation is a key process in solar flares that has extensively been investigated using the spectroscopic observations. However, direct soft X-ray (SXR) imaging of the process is rare, especially in remote brightenings associated with the primary flares that have recently attracted dramatic attention.} {We intend to find the evidence for chromospheric evaporation and figure out the cause of the process in sympathetic coronal bright points (CBPs), i.e., remote brightenings induced by the primary CBP.} {We utilise the high-cadence and high-resolution SXR observations of CBPs from the X-ray Telescope (XRT) aboard the Hinode spacecraft on 2009 August 23.} {We discover thermal conduction front propagating from the primary CBP, i.e., BP1, to one of the sympathetic CBPs, i.e., BP2 that is 60\arcsec away from BP1. The apparent velocity of the thermal conduction is $\sim$138 km s$^{-1}$. Afterwards, hot plasma flowed upwards into the loop connecting BP1 and BP2 at a speed of $\sim$76 km s$^{-1}$, a clear signature of chromospheric evaporation. Similar upflow was also observed in the loop connecting BP1 and the other sympathetic CBP, i.e., BP3 that is 80\arcsec away from BP1, though less significant than BP2. The apparent velocity of the upflow is $\sim$47 km s$^{-1}$. The thermal conduction front propagating from BP1 to BP3 was not well identified except for the jet-like motion also originating from BP1.} {We propose that the gentle chromospheric evaporation in the sympathetic CBPs were caused by thermal conduction originating from the primary CBP.}Comment: 9 pages, 5 figure

Blobs in recurring EUV jets

In this paper, we report our discovery of blobs in the recurrent and homologous jets that occurred at the western edge of NOAA active region 11259 on 2011 July 22. The jets were observed in the seven extreme-ultraviolet (EUV) filters of the Atmospheric Imaging Assembly (AIA) instrument aboard the Solar Dynamics Observatory (SDO). Using the base-difference images of the six filters (94, 131, 171, 211, 193, and 335 {\AA}), we carried out the differential emission measure (DEM) analyses to explore the thermodynamic evolutions of the jets. The jets were accompanied by cool surges observed in the H$\alpha$ line center of the ground-based telescope in the Big Bear Solar Observatory. The jets that had lifetimes of 20$-$30 min recurred at the same place for three times with interval of 40$-$45 min. Interestingly, each of the jets intermittently experienced several upward eruptions at the speed of 120$-$450 km s$^{-1}$. After reaching the maximum heights, they returned back to the solar surface, showing near-parabolic trajectories. The falling phases were more evident in the low-$T$ filters than in the high-$T$ filters, indicating that the jets experienced cooling after the onset of eruptions. We identified bright and compact blobs in the jets during their rising phases. The simultaneous presences of blobs in all the EUV filters were consistent with the broad ranges of the DEM profiles of the blobs ($5.5\le \log T\le7.5$), indicating their multi-thermal nature. The median temperatures of the blobs were $\sim$2.3 MK. The blobs that were $\sim$3 Mm in diameter had lifetimes of 24$-$60 s. To our knowledge, this is the first report of blobs in coronal jets. We propose that these blobs are plasmoids created by the magnetic reconnection as a result of tearing-mode instability and ejected out along the jets.Comment: 22 pages, 10 figure