A textbook example of magnetic flux emergence leading to EBs, UV bursts, surges and EUV signatures
Abstract
Small-scale eruptive phenomena (like Ellerman bombs (EBs), UV bursts, surges) constitute both a true challenge and an opportunity for progress in understanding the solar atmosphere since they involve very different layers from the photosphere to the low corona. In our work, we are aiming to characterize small-scale eruptive phenomena related to emerging flux regions. In particular, we use coordinated observations from the Swedish 1-m Solar Telescope (SST), the Interface Region Imaging Spectrograph (IRIS) and the Solar Dynamics Observatory (SDO, both HMI and AIA) to analyze an episode of magnetic flux emergence in an enhanced network that leads to an EB, a UV burst, a cool surge, and coronal signatures in the EUV. Through Milne-Eddington inversions of the Fe I 6302 Å line observed with SST/CRISP we obtain high-resolution (0.057"/pixel) magnetograms that allow us to reliably measure the magnetic field at the photosphere. A comparison with the corresponding SDO/HMI magnetograms reveals that this type of small-scale events are barely discernible in low-resolution (1") observations. During the emergence, a roundish dark bubble is visible in Ca II K 3933 Å at the location where the two opposite polarities of the emerging dipole are splitting apart. Several minutes later, indirect evidence of reconnection is found above the positive polarity of the dipole through the appearance of an EB in the wings of the {Hα} 6563 Å and Ca II K 3933 Å lines from SST, and also in the SDO/AIA 1600 and 1700 Å~data. Later, a surge shows up as an elongated structure visible in absorption in {Hα} and Ca II K, extending over 12 Mm projected size on the disk. The shape of the surge is also apparent as an absorption feature in the SDO/AIA channels. Simultaneously with the surge (and at the location where the EB had appeared earlier on) a UV burst is clearly discernible as a strong and bright emission feature both in IRIS/SJI 1400 and 2796 Å. Interestingly, this UV burst also has counterpart in SDO/AIA 94, 171, 193, 211, 304, and 335 Å, meaning that we can find multi-thermal plasma up to a few MK in the reconnection site. This observation clearly shows the impact of the emergence of new magnetic field from the photosphere through the chromosphere and transition region and up into the corona. In addition, it provides an illustrative case to test new realistic simulations.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.2531C