Hard X-ray impact on the ionosphere D-layer: new results from VLF measurements

<p>The ionospheric electron density reacts to a change of ionization condition by a time delay Δt. Appleton (1953) demonstrated that this time delay is inversely proportional to the product of the electron density Ne and recombination rate coefficient α. Thus, the evaluation of the time difference between the peak time of VLF emission, which is supposed to represent the instant of maximum ionization, and the ionization source's peak time provides an easy way to estimate α Ne. First used to evaluate the increase of electron density at noon from H α peak emission, this technic was also employed to estimate the recombination rate during solar flares. The GOES Soft X-ray emissions (i.e. in the range 1.5-12keV) are then considered to determine the ionising source peak time.</p><p>Based on VLF measurements obtained from the SUPERSID antenna installed at the Meudon site of the Paris Observatory (France), we computed each flare's time delay from January 2017. We benefit from the events of September 2017, the strongest from the last 10 years. We thus demonstrate the prominent role of Hard X-Rays in ionizing the D-layer of the ionosphere.  </p>

A full-dimensional model of ozone forming reaction: the absolute value of the recombination rate coefficient, its pressure and temperature dependencies

Rigorous calculations of scattering resonances in ozone are carried out for a broad range of rotational excitations with a detailed analysis of their properties and contribution into recombination process.

Effects of molecular rotation in low-energy electron collisions of

Measurements on the energetic structure of the dissociative recombination rate coefficient in the millielectronvolt range are described for ions produced in the lowest rotational levels by collisional cooling and stored as a fast beam in the magnetic storage ring TSR (Test Storage Ring). The observed resonant structure is consistent with that found previously at the storage ring facility CRYRING in Stockholm, Sweden; theoretical predictions yield good agreement on the overall size of the rate coefficient, but do not reproduce the detailed structure. First studies on the nuclear spin symmetry influencing the lowest level populations show a small effect different from the theoretical predictions. Heating processes in the residual gas and by collisions with energetic electrons, as well as cooling owing to interaction with cold electrons, were observed in long-time storage experiments, using the low-energy dissociative recombination rate coefficient as a probe, and their consistency with the recent cold measurements is discussed.