Wednesday, October 08, 2025 - 3:30 p.m. to 4:30 p.m.
Morse Hall, rm 301 -OR- Teams online
Speaker:
Dr. Yi-Hsin Liu
Associate Professor, Dartmouth College
Associate Professor, Dartmouth College
Abstract:
Three-dimensional (3D) particle-in-cell (PIC) simulations reveal rich kinetic features of magnetic reconnection X-lines. We show that the Hall effect, combined with the drift of current carriers, determines the internal asymmetry along the reconnection X-line in kinetic plasmas. This intrinsic 3D nature of reconnection offers an explanation for the opposite dawn-dusk asymmetry observed in Earth's and Mercury’s magnetotails—insights relevant to the NASA's MMS, MESSENGER, and ESA-JAXA's BepiColombo missions. With a larger system domain, PIC simulations further demonstrate that the X-line spreading develops a similar asymmetry, revealing a difference between the ion-drifting and electron-drifting sides.
In the second half of this talk, we will use a similar X-line asymmetry in guide-field reconnection to explain the formation of the auroral spirals in the ionosphere. In our model, the auroral arc develops through the precipitation of electrons accelerated by reconnection X-lines in the auroral acceleration region; note that it is not reconnection signatures from the tail, contrary to conventional wisdom. This model provides an explanation for the rotational sense of auroral spirals, which cannot be explained by local shear flows, and the rotational sense is opposite near Earth's north versus south poles.
A similar rotation may be identified in the auroral swirling pattern on Jupiter (i.e., Juno mission), and this scenario of reconnection within the auroral acceleration region may be of interest to NASA’s TRACERS mission. These findings highlight the rich features associated with three-dimensional (3D) reconnection X-lines, which could have applications across various space and astrophysical plasmas.
Free snacks and refreshments will be provided in Morse Hall beginning at 3:20 pm.
Schedule:
Check out the rest of this season's Space Science Seminar Series, as well as previous recordings here.
