Propagation of a sausage soliton in the solar lower atmosphere observed by Hinode/SOT

Abstract

Abstract Acoustic waves and pulses propagating from the solar photosphere upwards may quickly develop into shocks due to the rapid decrease of atmospheric density. However, if they propagate along a magnetic flux tube, then the non-linear steepening may be balanced by tube dispersion effects. This may result in the formation of a sausage soliton. The aim of this Letter is to report observational evidence of a sausage soliton in the solar chromosphere. A time series of the Caii H line obtained at the solar limb with the Solar Optical Telescope (SOT) on board Hinode is analysed. Observations show an intensity blob, which propagates from 500 to 1700 km above the solar surface with a mean apparent speed of 35 km s−1. The speed is much higher than the expected local sound speed, therefore the blob cannot be a simple pressure pulse. The blob speed, length-to-width ratio and relative intensity correspond to a slow sausage soliton propagating along a magnetic tube. The blob width increases with height corresponding to the magnetic tube expansion in the stratified atmosphere. Propagation of the intensity blob may be the first observational evidence of a slow sausage soliton in the solar atmosphere.