Diagnostics of Ellerman bombs with high-resolution spectral data

Abstract

Ellerman bombs (EBs) are tiny brightenings often observed near sunspots. The most impressive characteristic of the EB spectra is the two emission bumps in both wings of the Hα and Ca II 8542Å lines. High-resolution spectral data of three small EBs were obtained on 2013 June 6 with the largest solar telescope, the 1.6 meter New Solar Telescope (NST), at the Big Bear Solar Observatory. The characteristics of these EBs are analyzed. The sizes of the EBs are in the range of 0.3 ′′ -0.8 ′′ and their durations are only 3-5 minutes. Our semi-empirical atmospheric models indicate that the heating occurs around the temperature minimum region with a temperature increase of 2700-3000 K, which is surprisingly higher than previously thought. The radiative and kinetic energies are estimated to be as high as 5×10 25 -3.0×10 26 ergs despite the small size of these EBs. Observations of the magnetic field show that the EBs appeared just in a parasitic region with mixed polarities and accompanied by mass motions. Nonlinear force-free field extrapolation reveals that the three EBs are connected with a series of magnetic field lines associated with bald patches, which strongly implies that these EBs should be produced by magnetic reconnection in the solar lower atmosphere. According to the lightcurves and the estimated magnetic reconnection rate, we propose that there is a three phase process in EBs: pre-heating, flaring and cooling phases.

Solar Ellerman Bombs in 1D Radiative Hydrodynamics

“…This fits with observations reporting bi-directional jets at EB locations (Matsumoto et al 2008a;Watanabe et al 2011) and previous EB modeling attempts (Archontis & Hood 2009). A local temperature enhancement of 2000-3000 K also forms,and fits with previous estimates (Georgoulis et al 2002;Fang et al 2006;Isobe et al 2007;Archontis & Hood 2009;Li et al 2015). This situation, however, did not accurately model the Mg II h and k lines, which needed a more active starting atmosphere.…”

“…These temperature enhancements lead to intensity enhancements in the wings of the Hα and Ca II 8542 Å lines. Other EB studies also find similar temperature enhancements (200-3000 K) in the photosphere/temperature minimum region (Georgoulis et al 2002;Isobe et al 2007;Yang et al 2013;Hong et al 2014;Li et al 2015).…”

“…These events have also been observed in the wings of Ca II 8542 Å (Fang et al 2006;Socas-Navarro et al 2006;Pariat et al 2007;Li et al 2015;Vissers et al 2015), as well as in Ca II H images (Matsumoto et al 2008a;Hashimoto et al 2010). They show no observable enhancement in the core of these line profiles as these are formed in the overlying chromospheric canopy.…”

Magnetic Flux Cancellation in Ellerman Bombs

“…These temperature enhancements lead to intensity enhancements in the wings of the Hα and Ca II 8542 Å lines, while the line cores are formed higher in the chromosphere. Other studies of EBs also find similar temperature enhancements ranging from 200 to 3000 K in the photosphere/temperature minimum region (Georgoulis et al 2002;Isobe et al 2007;Yang et al 2013;Hong et al 2014;Li et al 2015).…”

RADYN Simulations of Non-thermal and Thermal Models of Ellerman Bombs

“…Different methods to invert the spectral lines including Hα, Ca II 8542 Å, and Fe I lines have been used to obtain the local temperature enhancement in the lower atmosphere. Both semi-empirical and two-cloud models show that the temperature enhancement is 600-3000 K (Fang et al 2006;Socas-Navarro et al 2006;Bello González et al 2013;Berlicki & Heinzel 2014;Hong et al 2014Hong et al , 2017Li et al 2015;Kondrashova 2016). Recently, the observation of UV bursts and the possible relationship between EBs and UV bursts is a very hot topic.…”