Aims. To investigate magnetic reconnection rates during the coalescence of two current loops in the solar chromosphere, by altering the neutralhydrogen to proton density ratio, ioniziation/recombination coefficients, collision frequency and relative helicity of the loops. Methods. 2.5D numerical simulations of the chromosphere were conducted using a newly developed two-fluid (ion-neutral) numer...

We report two-dimensional MHD simulations which demonstrate that photospheric 5-min oscillations can leak into the chromosphere inside small-scale vertical magnetic flux tubes. The results of our numerical experiments are compatible with those inferred from simultaneous spectropolarimetric observations of the photosphere and chromosphere obtained with the Tenerife Infrared Polarimeter (TIP) at ...

The natural state of the Solar chromosphere is very dynamic. Any photospheric disturbance will grow and naturally form shocks over the twenty scale-heights in density between the photosphere and the corona. Observations in the resonance lines from singly ionized calcium and recently in the ultraviolet region of the spectrum observed with the Solar and Heliospheric Observatory satellite also sho...

The energy for the coronal heating must be provided from the convection zone. However, the amount and the method by which this energy is transferred into the corona depend on the properties of the lower atmosphere and the corona itself. We review: (i) how the energy could be built in the lower solar atmosphere, (ii) how this energy is transferred through the solar atmosphere, and (iii) how the ...

Spectral diagnostic features formed in the solar chromosphere are few and difficult to interpret — they are neither formed in the optically thin regime nor in local thermodynamic equilibrium (LTE). To probe the state of the chromosphere, both from observations and theory, it is therefore necessary with modeling. I discuss both traditional semi-empirical modeling, numerical experiments illustrat...

We employ tomographic observations of a small region of plage to study the propagation of waves from the solar photosphere to the chromosphere using a Fourier phase-difference analysis. Our results show the expected vertical propagation for waves with periods of 3 minutes. Waves with 5-minute periods, i.e., above the acoustic cut-off period, are found to propagate only at the periphery of the p...

We have performed a detailed analysis of several hundreds Hα Ellerman bombs in the low chromosphere, above an emerging flux region. We find that Ellerman bombs may be small-scale, low-altitude, magnetic reconnection events that heat the low chromosphere in the active region. Their energy content varies between 10 erg and 10 erg, typical of subflaring activity.

I first review trends in current solar spectrometry and then concentrate on comparing various spectroscopic diagnostics of the solar chromosphere. Some are actually not at all chromospheric but just photospheric or clapotispheric and do not convey information on chromospheric heating, even though this is often assumed. Balmer Hα is the principal displayer of the closed-field chromosphere, but i...