During the 2010 rainy season in Yangbajing (4300 m above sea level) in Tibet, China, a long-duration count enhancement associated with thunderclouds was detected by a solar-neutron telescope and neutron monitors installed at the Yangbajing Comic Ray Observatory. The event, lasting for $40 min , was observed on July 22, 2010. The solar-neutron telescope detected significant -ray signals with energies >40 MeV in the event. Such a prolonged high-energy event has never been observed in association with thunderclouds, clearly suggesting that electron acceleration lasts for 40 min in thunderclouds. In addition, Monte Carlo simulations showed that >10 MeV rays largely contribute to the neutron monitor signals, while >1 keV neutrons produced via a photonuclear reaction contribute relatively less to the signals. This result suggests that enhancements of neutron monitors during thunderstorms are not necessarily clear evidence for neutron production, as previously thought.

We investigate the effects of two magnetic clouds on hourly cosmic-ray intensity profiles in the Forbush decrease events in November 2004 observed by 47 ground-based neutron-monitor stations. By using a wavelet decomposition, the start time of the main phase in a Forbush decrease event can be defined, and then clearer definitions of initial phase, main phase, and recovery phase are proposed. Our analyses suggest that the main phase of this Fd event precedes the arrival time of the first magnetic cloud by about three hours, and the Fds observed at the majority (39/47) of the stations were found to originate from the sheath region as indicated by large fluctuations in magnetic field vectors at 19:00 UT on 7 November 2004, regardless of the station location. In addition, about 45% of the onset times of the recovery phase in the Forbush decreases took place at 04:00 UT on 10 November, independent of the station position. The results presented here support the hypothesis that the sheath region between the shock and the magnetic cloud, especially the enhanced turbulent magnetic field, results in the scattering of cosmic-ray particles, and causes the following Forbush decreases. Analysis of variation profiles from different neutron monitors reveals the global simultaneity of this Forbush decrease event. Moreover, we infer that the interplanetary disturbance was asymmetric when it reached the Earth, inclined to the southern hemisphere. These results provide several observational constraints for more detailed simulations of the Forbush decrease events with time-dependent cosmic-ray modulation models.

The fast transitions between different types of quasi-periodic oscillations (QPOs) are generally observed in black hole transient sources (BHTs). We present a detailed study of the timing and spectral properties of the transitions of type-B QPOs in MAXI J1348–630, observed by Insight-HXMT. The fractional rms variability–energy relationship and energy spectra reveal that type-B QPOs probably originate from jet precession. Compared to a weak power-law dominated power spectrum, when type-B QPOs are present, the corresponding energy spectrum shows an increase in the Comptonization component and the need for the xillverCp component, and a slight increase in the height of the corona when using the relxilllp model. Therefore, we suggest that a coupled inner disk-jet region is responsible for the observed type-B QPO transitions. The timescale for the appearance/disappearance of type-B QPOs is either long or short (seconds), which may indicate instability of the disk-jet structure. For these phenomena, we hypothesize that the Bardeen–Petterson effect causes the disk-jet structure to align with the BH spin axis or that the disappearance of small-scale jets bound by the magnetic flux tubes leads to the disappearance of type-B QPOs. We observed three events regarding the B/C transitions, one of which occurred over a short time period from ∼9.2 Hz (C) to ∼4.8 Hz (B). The energy spectral analysis for the other two transitions shows that when type-C QPO is present, the Comptonization flux is higher, the spectrum is harder, and the inner radius of the disk changes insignificantly. We suggest that type-C QPOs probably originate from relatively stronger jets or the corona.