Influence of coronal holes on CMEs in causing SEP events

The issue of the influence of coronal holes （CHs） on coronal mass ejections （CMEs） in causing solar energetic particle （SEP） events is revisited. It is a continuation and extension of our previous work, in which no evident effects of CHs on CMEs in generating SEPs were found by statistically investigating 56 CME events. This result is consistent with the conclusion obtained by Kahler in 2004. We extrapolate the coronal magnetic field, define CHs as the regions consisting of only open magnetic field lines and perform a similar analysis on this issue for 76 events in total by extending the study interval to the end of 2008. Three key parameters, CH proximity, CH area and CH relative position, are involved in the analysis. The new result confirms the previous conclusion that CHs did not show any evident effect on CMEs in causing SEP events.

Flares and magnetic non-potentiality of NOAA AR 11158

Magnetic non-potentiality is important for understanding flares and other solar activities in active regions （ARs）. Five non-potential parameters, i.e. electric current, current helicity, source field, photospheric free energy, and angular shear, are calculated to quantify the non-potentiality of NOAA AR 11158. Benefitting from the high spatial resolution, high cadence and continuous temporal coverage of vector mag- netograms from the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory, both the long-term evolution of the AR and the rapid change during flares are studied. We confirm that, compared with the magnetic flux, the magnetic non-potentiality has a closer connection with the flare, and the emerging flux regions are important for understanding the magnetic non-potentiality and flares. The main re- suits are as follows. （1） The vortex in the source field directly displays the deflection of the horizontal magnetic field. The deflection corresponds to the fast rotating sunspot with a time delay, which suggests that the sunspot rotation leads to an increase in the non-potentiality. （2） Two areas that have evident changes in the azimuth of the vector magnetic field are found near the magnetic polarity inversion line. The change rates of the azimuth are about 1.3° h-1 and 3.6° h-1, respectively. （3） Rapid and prominent increases are found in the variation of helicity during four flares in the regions where their initial brightening occurs. The recovery of the increases takes 3-4 h for the two biggest flares （X2.2 and M6.6）, but only takes about 2 h for the two other smaller flares （M2.2 and M1.6）.

Kinematics and amplitude evolution of global coronal extreme ultraviolet waves

With the observations of the Solar-Terrestrial Relations Observatory （STEREO） and the Solar Dynamics Observatory （SDO）, we analyze in detail the kine- matics of global coronal waves together with their intensity amplitudes （so-called ＂perturbation profiles＂）. We use a semi-automatic method to investigate the pertur- bation profiles of coronal waves. The location and amplitude of the coronal waves are calculated over a 30~ sector on the sphere, where the wave signal is strongest. The position with the strongest perturbation at each time is considered as the location of the wave front. In all four events, the wave velocities vary with time for most of their lifetime, up to 15 rain, while in the event observed by the Atmospheric Imaging Assembly there is at, additional early phase with a much higher velocity. The velocity varies greatly between different waves from 216 to 440 km s-1. The velocity of the two waves initially increases, subsequently decreases, and then increases again. Two other waves show a deceleration followed by an acceleration. Three categories of am- plitude evolution of global coronal waves are found for the four events. The first is that the amplitude only shows a decrease. The second is that the amplitude initially increases and then decreases, and the third is that the amplitude shows an orderly in- crease, a decrease, an increase again and then a decrease. All the extreme ultraviolet waves show a decrease in amplitude while propagating farther away, probably because the driver of the global coronal wave （coronal mass ejection） is moving farther away from the solar surface.

An empirical method to correct the saturation seen in the SOHO/MDI magnetograms

The magnetic field of the umbrae is sometimes found to be saturated in the magnetograms taken by the Michelson Doppler Imager （MDI） onboard the Solar and Heliospheric Observatory （SOHO）. It is suggested that the combination of the low intensity of sunspot umbrae and the limitation of the 15-bit onboard numerical data acquisition leads to this saturation. In this paper, we propose to use the MDI＇s intensity data to correct this saturation. This method is based on the well-established relationship between the continuum intensity and the magnetic field （the so-called I-B relationship）. A comparison between the corrected magnetic field and the data taken by the Stokes-Polarimeter of the Solar Optical Telescope （SOT/SP） onboard Hinode shows a reasonable agreement, suggesting that this correction is effective.

Interpretations of the cosmic ray secondary-toprimary ratios measured by DAMPE

Precise measurements of the boron-to-carbon and boron-to-oxygen ratios by DAMPE show clear hardenings around 100 GeV/n,which provide important implications on the production,propagation,and interaction of Galactic cosmic rays.In this work we investigate a number of models proposed in literature in light of the DAMPE findings.These models can roughly be classified into two classes,driven by propagation effects or by source ones.Among these models discussed,we find that the re-acceleration of cosmic rays,during their propagation,by random magnetohydrodynamic waves may not reproduce sufficient hardenings of B/C and B/O,and an additional spectral break of the diffusion coefficient is required.The other models can properly explain the hardenings of the ratios.However,depending on simplifications assumed,the models differ in their quality in reproducing the data in a wide energy range.The models with significant re-acceleration effect will under-predict low-energy antiprotons but over-predict low-energy positrons,and the models with secondary production at sources over-predict high-energy antiprotons.For all models high-energy positron excess exists.