* Astronomy

Blobrana · L

RE: Ellerman Bombs

Blobrana · L

Title: Ellerman Bombs with Jets: Cause and Effect
Author: A. Reid, M. Mathioudakis, E. Scullion, J.G. Doyle, S. Shelyag, P. Gallagher

Ellerman Bombs (EBs) are thought to arise as a result of photospheric magnetic reconnection. We use data from the Swedish 1-m Solar Telescope (SST), to study EB events on the solar disk and at the limb. Both datasets show that EBs are connected to the foot-points of forming chromospheric jets. The limb observations show that a bright structure in the H-alpha blue wing connects to the EB initially fuelling it, leading to the ejection of material upwards. The material moves along a loop structure where a newly formed jet is subsequently observed in the red wing of H-alpha. In the disk dataset, an EB initiates a jet which propagates away from the apparent reconnection site within the EB flame. The EB then splits into two, with associated brightenings in the inter-granular lanes (IGLs). Micro-jets are then observed, extending to 500 km with a lifetime of a few minutes. Observed velocities of the micro-jets are approximately 5-10 km s^-1, while their chromospheric counterparts range from 50-80 km s^-1. MURaM simulations of quiet Sun reconnection show that micro-jets with similar properties to that of the observations follow the line of reconnection in the photosphere, with associated H-alpha brightening at the location of increased temperature.

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Blobrana · L

Title: Statistical Analysis of Small Ellerman Bomb Events
Authors: C. J. Nelson, J. G. Doyle, R. Erdelyi, Z. Huang, M. Madjarska, M. Mathioudakis, S. Mumford, K. Reardon

The properties of Ellerman bombs (EBs), small-scale brightenings in the H-alpha line wings, have proved difficult to establish due to their size being close to the spatial resolution of even the most advanced telescopes. Here, we aim to infer the size and lifetime of EBs using high-resolution data of an emerging active region collected using the Interferometric BIdimensional Spectrometer (IBIS) and Rapid Oscillations of the Solar Atmosphere (ROSA) instruments as well as the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We develop an algorithm to track EBs through their evolution, finding that EBs can often be much smaller (around 0.3") and shorter lived (less than 1 minute) than previous estimates. A correlation between G-band magnetic bright points and EBs is also found. Combining SDO/HMI and G-band data gives a good proxy of the polarity for the vertical magnetic field. It is found that EBs often occur both over regions of opposite polarity flux and strong unipolar fields, possibly hinting at magnetic reconnection as a driver of these events. The energetics of EB events is found to follow a power-law distribution in the range of "nano-flare" (10^{22-25} ergs).

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