0000000000087848
AUTHOR
Enrico Landi
showing 6 related works from this author
The role of radiative losses in the late evolution of pulse-heated coronal loops/strands
2012
Radiative losses from optically thin plasma are an important ingredient for modeling plasma confined in the solar corona. Spectral models are continuously updated to include the emission from more spectral lines, with significant effects on radiative losses, especially around 1 MK. We investigate the effect of changing the radiative losses temperature dependence due to upgrading of spectral codes on predictions obtained from modeling plasma confined in the solar corona. The hydrodynamic simulation of a pulse-heated loop strand is revisited comparing results using an old and a recent radiative losses function. We find significant changes in the plasma evolution during the late phases of plas…
Bright hot impacts by erupted fragments falling back on the Sun: UV redshifts in stellar accretion
2014
A solar eruption after a flare on 7 Jun 2011 produced EUV-bright impacts of fallbacks far from the eruption site, observed with the Solar Dynamics Observatory. These impacts can be taken as a template for the impact of stellar accretion flows. Broad red-shifted UV lines have been commonly observed in young accreting stars. Here we study the emission from the impacts in the Atmospheric Imaging Assembly's UV channels and compare the inferred velocity distribution to stellar observations. We model the impacts with 2D hydrodynamic simulations. We find that the localised UV 1600A emission and its timing with respect to the EUV emission can be explained by the impact of a cloud of fragments. The …
Bright hot impacts by erupted fragments falling back on the Sun: a template for stellar accretion.
2013
Impacts of falling fragments observed after the eruption of a filament in a solar flare on 7 June 2011 are similar to those inferred for accretion flows on young stellar objects. As imaged in the ultraviolet (UV)-extreme UV range by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory, many impacts of dark, dense matter display uncommonly intense, compact brightenings. High-resolution hydrodynamic simulations show that such bright spots, with plasma temperatures increasing from ~10(4) to ~10(6) kelvin, occur when high-density plasma (>>10(10) particles per cubic centimeter) hits the solar surface at several hundred kilometers per second, producing high-energy emission as …
Temperature Distribution of a Non-flaring Active Region from Simultaneous Hinode XRT and EIS Observations
2011
We analyze coordinated Hinode XRT and EIS observations of a non-flaring active region to investigate the thermal properties of coronal plasma taking advantage of the complementary diagnostics provided by the two instruments. In particular we want to explore the presence of hot plasma in non-flaring regions. Independent temperature analyses from the XRT multi-filter dataset, and the EIS spectra, including the instrument entire wavelength range, provide a cross-check of the different temperature diagnostics techniques applicable to broad-band and spectral data respectively, and insights into cross-calibration of the two instruments. The emission measure distribution, EM(T), we derive from the…
Post-flare Ultraviolet Light Curves Explained with Thermal Instability of Loop Plasma
2012
In the present work, we study the C8 flare that occurred on 2000 September 26 at 19:49 UT and observed by the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation spectrometer from the beginning of the impulsive phase to well beyond the disappearance in the X-rays. The emission first decayed progressively through equilibrium states until the plasma reached 2-3 MK. Then, a series of cooler lines, i.e., Ca X, Ca VII, Ne VI, O IV, and Si III (formed in the temperature range log T = 4.3-6.3 under equilibrium conditions), are emitted at the same time and all evolve in a similar way. Here, we show that the simultaneous emission of lines with such a different forma…
Monte Carlo Markov Chain DEM reconstruction of isothermal plasmas
2012
In this paper, we carry out tests on the Monte Carlo Markov Chain (MCMC) technique with the aim of determining: 1) its ability to retrieve isothermal plasmas from a set of spectral line intensities, with and without random noise; 2) to what extent can it discriminate between an isothermal solution and a narrow multithermal distribution; and 3) how well it can detect multiple isothermal components along the line of sight. We also test the effects of 4) atomic data uncertainties on the results, and 5) the number of ions whose lines are available for the DEM reconstruction. We find that the MCMC technique is unable to retrieve isothermal plasmas to better than Delta log T = 0.05. Also, the DEM…