Solar spikes are radio bursts closely associated with the spontaneous phase of solar flares. This leads researchers to recommend that solar spikes represent primary energy release events during solar flares.
Earlier research studies have suggested the electron-cyclotron-maser emission (ECME) driven by energetic electrons with the loss-cone distribution to be the emission mechanism of spikes (Holman et al. 1980). Yet, the loss-cone maser primarily delights the basic X mode (X1), and it is challenging for X1 to go through the second harmonic absorption layer throughout its escape from the source (Melrose & & Dulk 1982). This provides the so-called getting away problem of ECME when it is applied to solar radio spikes as well as other kinds of radio bursts connected with similar magnetic setups.
Another problem is that the majority of earlier studies used recommended analytical velocity distribution function (VDF) while any solar radio bursts are an effect of a multiscale procedure beginning with massive magnetic eruptive activities in the huge to MHD scale, followed by particle acceleration via magnetic reconnection or shocks in the particle kinetic scale and additional excitation and propagation of electro-magnetic radiations. In this research study, as a beginning point to bridge the large-scale dynamics and small plasma kinetic maser instabilities connected with solar radio bursts, in specific, solar spikes, we established a mathematical scheme integrating techniques consisting of (1) the magnetic field extrapolation to explain the magnetic configuration of a regular loop within a well-studies active area (see Figure 1); (2) the guiding-center (GC) approach to presume the temporal advancement of VDFs along different areas of the loop while taking the impact of pitch-angle scattering into account; and (3) the particle-in-cell (PIC) simulation to even more check out the kinetic instabilities driven by electrons with the gotten VDFs. This represents a substantially simplified technique for the proposed research study.
Solar spikes are radio bursts closely associated with the spontaneous stage of solar flares. This leads researchers to suggest that solar spikes represent elementary energy release events throughout solar flares.
Another problem is that the majority of earlier research studies employed recommended analytical speed circulation function (VDF) while any solar radio bursts are a consequence of a multiscale process starting from large-scale magnetic eruptive activities in the huge to MHD scale, followed by particle acceleration through magnetic reconnection or shocks in the particle kinetic scale and further excitation and proliferation of electromagnetic radiations. In this research study, as a starting point to bridge the massive dynamics and small-scale plasma kinetic maser instabilities associated with solar radio bursts, in particular, solar spikes, we developed a mathematical scheme integrating techniques consisting of (1) the magnetic field projection to explain the magnetic setup of a typical loop within a well-studies active area (see Figure 1); (2) the guiding-center (GC) method to presume the temporal development of VDFs along different sections of the loop while taking the effect of pitch-angle scattering into account; and (3) the particle-in-cell (PIC) simulation to further explore the kinetic instabilities driven by electrons with the gotten VDFs. Efficient amplification of X2 prefers the escape of ECME radiation from the corona, and this effectively lowers the restriction of applying ECME to solar spikes.
Figure 1–( a) The magnetogram of HMI/SDO for AR 11283 prior to the eruption of the significant X2.1 flare on 2011 September 6, overplotted with field lines given by the NLFFF extrapolation; (b) the picked loop structure for the GC simulation of energetic electrons. The color in panels (b) represents the field strength (in units of Gauss). The letters “A– D” represent the sections within which VDFs will be examined, and the letter “I” represents the region of injection.
It was discovered that the VDFs of energetic electrons injected from the loop top manifest intriguing strip-like feature with significant positive speed gradient, together with the familiar loss-cone function (see upper panels of Figure 2). The strip-like functions of VDFs are formed due to the bouncing movement of energetic electrons during the early stage of the VDF relaxation toward a strong loss-cone distribution. According to further PIC simulations fed by the corresponding VDFs in plasmas with the specification setup of ωpe/ ωce = 0.25, the strip-like function is essential for efficient excitation of ECME at harmonic X mode (in the weak scattering case), while the loss-cone feature can be efficient in interesting the essential X mode (in the strong-scattering case). See Figure 2 for the PIC outcomes.
Efficient amplification of X2 favors the escape of ECME radiation from the corona, and this successfully lowers the restriction of using ECME to solar spikes. The research study provides brand-new insight into how escaping radiation, in particular, the harmonic X mode, can be created within a coronal loop. The circumstance presented here may likewise work to other types of radio bursts generated within similar astrophysical and space scenarios.
Figure 2– (a-c) VDFs at t = 1000 wpe-1 acquired by the PIC simulation for cases with numerous levels of scattering: W for weak, M for moderate, and S for strong scattering case; (d-f) temporal profiles of energies of different wave modes (X1, x2, and z), stabilized to the total energy of energetic electrons (Ek0).
This nugget is based on the paper by Yousefzadeh, M., Ning, H., & & Chen, Y. 2021, APJ, 909 3 doi: 10.3847/ 1538-4357/ abd8d5.
Recommendations:.
Holman, G. D., Eichler, D., & & Kundu, M. R. 1980, in IAU Symp. 86, Radio Physics of the Sun, ed. M. R. Kundu & & T. E. Gergely (Cambridge: Cambridge Univ.
Press), 457. Melrose, & D. B., & Dulk, G. A. 1982, ApJ, 259, 844.
* Full list of Authors: Mehdi Yousefzadeh, Hao Ning, and Yao Chen.