Impulsive radio and hard X-ray emission from an M-class flare

Abstract

Context. Impulsive radio and hard X-ray emission from large solar flares are usually attributed to a hard distribution of high-energy electrons accelerated in the energy dissipation process of magnetic reconnection. Aims. We report the detection of impulsive radio and hard X-ray emissions produced by a population of energetic electrons with a very soft distribution in an M-class flare: SOL2015-08-27T05:45 . Methods. The absence of impulsive emission at 34 GHz and hard X-ray emission above 50 keV and the presence of distinct impulsive emission at 17 GHz and lower frequencies and in the 25-50 keV X-ray band imply a very soft distribution of energetic electrons producing the impulsive radio emission via the gyro-synchrotron process, and impulsive X-rays via bremsstrahlung. Results. The spectrum of the impulsive hard X-ray emission can be fitted equally well with a power-law model with an index of ∼6.5 or a super-hot thermal model with a temperature as high as 100 MK. Imaging observations in the extreme-UV and X-ray bands and extrapolation of the magnetic field structure using a nonlinear force-free model show that energetic electrons trapped in coronal loops are responsible for these impulsive emissions. Conclusions. Since the index of the power-law model is nearly constant during the impulsive phase, the power-law distribution or the super-hot component should be produced by a bulk energization process such as the Fermi and betatron acceleration of collapsing magnetic loops.

A “one-for-three” strategy through a facile one-step hydrothermal engineering of commercial MoO3 for high-performance proton storage

“…3g. 19,22,[36][37][38][39][40][41][42][43][44][45][46][47] Furthermore, 55.3% of the initial capacitance (723.1 F g À1 , 130.6 mA h g À1 ) can be preserved even when the current density increases by 50-fold, and the discharge process is completed quickly within 9.4 s. This rate performance is much higher than that of pristine MoO 3 (25.9% capacitance retention) and the P0-MoO 3 electrode without coating of PANI (11.1% capacitance retention).…”

“…Notably, the P100-MoO 3 //NAC PBSH device delivers a maximum energy density of 43.3 W h kg À1 (at 1.0 A g À1 ) at a power density of 800.0 kW kg À1 , which is higher than that of the P100-MoO 3 //AC PBSH device and higher than those of most recently reported MoO 3 -based electrochemical devices. 19,23,44,46,49,50 The self-discharging time is a critical parameter to evaluate the performance of the PBSH device. To evaluate the performance of our PBSH device, the self-discharge test was carried out by fully charging the device to 1.60 V and then recording the fully discharging process as shown in Fig.…”

“…However, the conventional method of compounding MoO 3 with other metal materials (such as NiMoO 4 and CuO) is not suitable in hydrogen-ion electrolytes due to the dissolution issue. 19,20 Besides, the formation of defects in MoO 3 requires high temperature and/or strong reductants which makes the preparation process very complicated. 21 Moreover, coating of CNTs, MXene, or rGO on MoO 3 requires multiple preparation steps and increases the preparation cost.…”

Non-thermal electron energization during the impulsive phase of an X9.3 flare revealed by Insight-HXMT

“…Thermal bremsstrahlung emission from hot corona plasma contributes to the gradual phase of flares in general, and the intensive impulsive emission mainly comes from gyrosynchrotron emission process (Zhang et al 2018). To quantify the non-thermal energy releasing process from the X9.3 flare, especially the non-thermal energetic electrons which were the primary contributor of the impulsive peak phase for hard X-ray emission, we have to combine the limited hard x-ray observations and radio observation to build an evolutionary gyrosynchrotron source model.…”

X-ray fine structure of a limb solar flare revealed by Insight-HXMT, RHESSI and Fermi

“…In this paper, we presented joint observations of a limb flare on 2017 July 3 by RHESSI, FERMI and Insight-HXMT and SDO/AIA to study the hard X-ray evolution during the flare peak phase. The hard X-ray light curves around the peak phase showed a very gradual variation pattern, indicating that the energy release from magnetic reconnection processes tended to be gentle compared with impulsive flares (Zhang et al 2018(Zhang et al , 2021. The RHESSI hard X-ray imaging only showed a single foot-point, so we do not see the loop-top source and even another footpoint at all energy ranges which are predicted by a standard cups flare model.…”