Solar Origin of Compressive Alfvénic Spikes/Kinks as Observed by Parker Solar Probe

• Published in: Astrophysical journal. Letters Vol. 913; no. 1; p. L14
• Main Authors: He, Jiansen, Zhu, Xingyu, Yang, Liping, Hou, Chuanpeng, Duan, Die, Zhang, Lei, Wang, Ying
• Format: Journal Article
• Language: English
• Published: Austin The American Astronomical Society 01.05.2021; IOP Publishing
• Subjects: Alfven waves; Closed loops; Conduction heating; Density; Funnels; Heat flux; Jet flow; Magnetic fields; Magnetic reconnection; Magnetohydrodynamics; Plasmas (physics); Propagation modes; Solar atmosphere; Solar magnetic reconnection; Solar probes; Solar wind; Spikes; Tubes; Wave propagation
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/abf83d

The solar wind is found by the Parker Solar Probe to be abundant with Alfvénic velocity spikes and magnetic field kinks. Temperature enhancement is another remarkable feature associated with the Alfvénic spikes. How the prototype of these coincident phenomena is generated intermittently in the source region is an important and wide-ranging subject. Here we propose a new model introducing guide-field discontinuity into the interchange magnetic reconnection between open funnels and closed loops with different magnetic helicities. The modified interchange reconnection model not only can accelerate jet flows from the newly opening closed loop but also can excite and launch Alfvénic wave pulses along the newly reconnected and post-reconnected open flux tubes. We find that the modeling results can reproduce the following observational features: (1) Alfvén disturbance is pulsive in time and asymmetric in space; (2) Alfvénic pulse is compressive with temperature enhancement and density variation inside the pulse. We point out that three physical processes co-happening with Alfvén wave propagation can be responsible for the temperature enhancement: (a) convection of heated jet flow plasmas (decrease in density), (b) propagation of compressive slow-mode waves (increase in density), and (c) conduction of heat flux (weak change in density). We also suggest that the radial nonlinear evolution of the Alfvénic pulses should be taken into account to explain the formation of magnetic switchback geometry.