Speaker
Shahin Jafarzadeh
(Institute of Theoretical Astrophysics, University of Oslo)
Description
We characterise magnetohydrodynamics (MHD) waves in small magnetic elements and
investigate their propagation in the solar atmosphere by exploiting coordinated
observations with the Swedish 1 m Solar Telescope (SST) and the Interface Region
Imaging Spectrograph (IRIS). We use wavelet transform to analyse (horizontal)
displacement oscillations in magnetic bright points in several passbands sampling
various heights within the solar photosphere and chromosphere. Cross correlations
between wavelet power spectra of the transverse oscillations in the same magnetic
elements observed at different atmospheric heights, and of oscillations in emission
peaks of the IRIS Mg II H & K lines result in positive phase lags at high frequencies
(up to 30 mHz). These reveal a direct evidence for upward propagation of transverse
waves in the magnetic elements under study, and more importantly, an evident heating
signature at the heights sampled by the Mg II H & K lines, i.e., the upper
chromosphere. Together with estimates of height differences between the atmospheric
layers sampled by the employed spectral bands (and hence phase speeds of the
propagating waves) as well as the determined velocity amplitudes, we estimate an
energy flux on the order of 36 kW/m^2, that is sufficient to heat the quiet
chromosphere. The heating signatures from the IRIS spectra suggest that this energy,
or at least a fraction of that, is likely released in the upper chromosphere.
Primary author
Shahin Jafarzadeh
(Institute of Theoretical Astrophysics, University of Oslo)
