Unexpectedly Large Lorentz-Force Impulse Observed During a Solar Eruption
Abstract
For fast coronal mass ejections (CMEs), the acceleration phase takes place in the low corona; the momentum process is presumably dominated by the Lorentz force. Using ultra-high-cadence vector magnetic data from the Helioseismic and Magnetic Imager (HMI) and numerical simulations, we show that the observed fast-evolving photospheric field can be used to characterize the impulse of the Lorentz force during a CME. While the peak Lorentz force concurs with the maximum ejecta acceleration, the observed total force impulse surprisingly exceeds the CME momentum by over an order of magnitude. We conjecture that most of the Lorentz force impulse is "trapped" in the thin layer of the photosphere above the HMI line-formation height and is counter-balanced by gravity. This implies a consequent upward plasma motion which we coin "gentle photospheric upwelling". The unexpected effect dominates the momentum processes, but is negligible for the energy budget, suggesting a complex coupling between different layers of the solar atmosphere during CMEs.
- Publication:
-
Solar Heliospheric and INterplanetary Environment (SHINE 2016)
- Pub Date:
- July 2016
- Bibcode:
- 2016shin.confE.158S