Excitation of Slow-Modes in Network Magnetic Elements Through Magnetic Pumping

TL;DR

This paper identifies a new mechanism where convective downdrafts excite slow magnetoacoustic modes in solar magnetic flux elements, leading to shock waves that could produce dynamic fibrils, based on radiation magnetohydrodynamic simulations.

Contribution

It reveals a novel excitation process for slow modes in magnetic elements driven by external convective downdrafts, mediated by inertial forces, not previously described.

Findings

Convective downdrafts excite slow modes in magnetic flux concentrations.

The process involves inertial forces coupling external downdrafts to internal plasma motions.

Resulting shock waves may produce observable dynamic fibrils in the solar atmosphere.

Abstract

From radiation magnetohydrodynamic simulations of the solar atmosphere we find a new mechanism for the excitation of longitudinal slow modes within magnetic flux concentrations. We find that the convective downdrafts in the immediate surroundings of magnetic elements are responsible for the excitation of slow modes. The coupling between the external downdraft and the plasma motion internal to the flux concentration is mediated by the inertial forces of the downdraft that act on the magnetic flux concentration. These forces, in conjunction with the downward movement, pump the internal atmosphere in the downward direction, which entails a fast downdraft in the photospheric and chromospheric layers of the magnetic element. Subsequent to the transient pumping phase, the atmosphere rebounds, causing a slow mode traveling along the magnetic flux concentration in the upward direction. It develops into a shock wave in chromospheric heights, possibly capable of producing some kind of dynamic fibril. We propose an observational detection of this process.