Figure 5 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Synthetic SDO/AIA images for Case A2 * with the classical Spitzer thermal conduction coefficient. Rows (a) and (b) show the total count rates (DN per second per pixel) for the EI and NEI results, respectively. (c) shows the relative difference (I nei − I ei )/(I nei + I ei ) between the NEI and EI count rates.
Source publication
Nonequilibrium ionization (NEI) is essentially required for astrophysical plasma diagnostics once the plasma status departs from the assumption of ionization equilibrium. In this work, we perform fast NEI calculations combined with magnetohydrodynamic (MHD) simulations and analyze the ionization properties of a Petschek-type magnetic reconnection c...
Contexts in source publication
Context 1
... the AIA intensity that counts all emission lines from the above 14 elements is calculated at each cell of the MHD simulations. Figure 5 shows the synthetic SDO/AIA count rate for Case A2 * with the thermal halo structures outside the shock front. The first row shows the AIA intensities under the assumption of EI and the second row shows the results using the NEI results, respectively. ...
Context 2
... SDO/AIA images for Case A2 applying conduction flux limitation. The panels are defined the same as in Figure 5. assumption of EI, the thermal halo can be clearly recognized in all SDO/AIA channels because the emission intensity is only temperature dependent ( Figure 5(a)). ...
Context 3
... SDO/AIA images for Case A2 applying conduction flux limitation. The panels are defined the same as in Figure 5. assumption of EI, the thermal halo can be clearly recognized in all SDO/AIA channels because the emission intensity is only temperature dependent ( Figure 5(a)). It appears as significantly low emission sheathes outside the Petschek-type shock fronts in the AIA 94,171,193,211, and 335 Å channels. ...
Context 4
... the NEI synthetic images show that the signal of the thermal halo regions is significantly weaker than that under the assumption of EI. As shown in Figure 5(b), the low-emission sheath is hard to observe in AIA 131 Å, which causes a narrower bright reconnection region compared to the EI image in this channel. In contrast, the AIA 94 Å and AIA 211 Å maps generally show a wider bright reconnection current sheet region compared with the EI images due to the contribution of the effects of NEI on the thermal halo regions. ...
Context 5
... contrast, the AIA 94 Å and AIA 211 Å maps generally show a wider bright reconnection current sheet region compared with the EI images due to the contribution of the effects of NEI on the thermal halo regions. We can see the effects of NEI on the intensities from the scaled relative difference ((I nei − I ei )/(I nei + I ei )) of the synthetic emission intensity between the NEI and EI cases (see the third row of Figure 5). Inside the reconnection region, the assumption of EI causes underestimated count rates in the AIA 94, 131, and ...
Similar publications
We performed two data-based magnetohydrodynamic (MHD) simulations for solar active region 12371, which produced an M6.5 flare. The first simulation is a full data-driven simulation where the initial condition is given by a nonlinear force-free field (NLFFF). This NLFFF was extrapolated from photospheric magnetograms approximately 1 hr prior to the...
Citations
... The rapid heating or cooling of plasma can lead to departures from ionisation equilibrium; a state when the plasma ionic composition does not reflect its electron temperature, e.g., Refs. [57,[81][82][83][84][85][86]. This transient ionisation in turn can affect other diagnostics, e.g., Refs. ...
Particle acceleration, and the thermalisation of energetic particles, are fundamental processes across the universe. Whilst the Sun is an excellent object to study this phenomenon, since it is the most energetic particle accelerator in the Solar System, this phenomenon arises in many other astrophysical objects, such as active galactic nuclei, black holes, neutron stars, gamma ray bursts, solar and stellar coronae, accretion disks and planetary magnetospheres. Observations in the Extreme Ultraviolet (EUV) are essential for these studies but can only be made from space. Current spectrographs operating in the EUV use an entrance slit and cover the required field of view using a scanning mechanism. This results in a relatively slow image cadence in the order of minutes to capture inherently rapid and transient processes, and/or in the spectrograph slit ‘missing the action’. The application of image slicers for EUV integral field spectrographs is therefore revolutionary. The development of this technology will enable the observations of EUV spectra from an entire 2D field of view in seconds, over two orders of magnitude faster than what is currently possible. The Spectral Imaging of the Solar Atmosphere (SISA) instrument is the first integral field spectrograph proposed for observations at ∼180 Å combining the image slicer technology and curved diffraction gratings in a highly efficient and compact layout, while providing important spectroscopic diagnostics for the characterisation of solar coronal and flare plasmas. SISA’s characteristics, main challenges, and the on-going activities to enable the image slicer technology for EUV applications are presented in this paper.
... That result is somewhat surprising, in that one might expect strong heating and large populations of energetic electrons in reconnection current sheets, leading to elevated values of 〈Q〉 in impulsive events. High charge states in current sheets are observed in EUV images and UV spectra (Innes et al. 2003;Ciaravella & Raymond 2008;Reeves & Golub 2011;Warren et al. 2018) and predicted by models (Shen et al. 2013(Shen et al. , 2023. The heating may be less intense in jets than in flares; Joshi et al. (2020) found temperatures of 1.4-1.8 ...
An important aspect of solar energetic particle (SEP) events is their source populations. Elemental abundance
enhancements of impulsive SEP events, originating in presumed coronal reconnection episodes, can be fitted to
steep power laws of A/Q, where A and Q are the atomic mass and ionic charge. Since thermal electron energies are
enhanced and nonthermal electron distributions arise in the reconnection process, we might expect that ionic
charge states Q would be increased through ionization interactions with those electron populations during the
acceleration process. The temperature estimated from the SEPs corresponds to the charge state during the
acceleration process, while the actual charge state measured in situ may be modified as the SEPs pass through the
corona. We examine whether the temperature estimation from the A/Q would differ with various κ values in a κ
function representing high-energy tail deviating from a Maxwellian velocity distribution. We find that the
differences in the A/Q between a Maxwellian and an extreme κ distribution are about 10%–30%. We fit power-law
enhancement of element abundances as a function of their A/Q with various κ values. Then, we find that the
derived source region temperature is not significantly affected by whether or not the electron velocity distribution
deviates from a Maxwellian, i.e., thermal, distribution. Assuming that electrons are heated in the acceleration
region, the agreement of the SEP charge state during acceleration with typical active region temperatures suggests
that SEPs are accelerated and leave the acceleration region in a shorter time than the ionization timescale.
