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Hot explosionsin the cool solar atmosphere Hardi PeterMax Planck Institute for Solar System ResearchGttingen

H. Tian, W. Curdt, D. Schmit, D. Innes, B. De Pontieu, & IRIS team

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Emerging AR (24. Sep. 2013): IRIS & SDOthree bright featureswith lifetimes of > 5 minSi IV spectroheliogramIRIS 1400 AIA 171 AIA 304 AIA 1600 HMI Blos70 x 35

these events happen at places of flux cancellation2Normal spectrum: average plage

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Strange spectra: in a bombabsorption lines !~5 km/s blueshiftmissing O IV linesoptically thinbi-directional flowsame profile envelopein Mg II, C II, Si IV !!4Density diagnostics

Doppler shift relative to target line rest wavelength [km/s] spectral radiance [DN / pixel] O IV1399.77O IV1401.16

O IV 1400O IV 1401 0.26 ne 4 x 1010 cm-3traditional density diagnostics:ratio of forbidden lineswith IRIS:O IV lines around 1400 Si IV1403.77

O IV 1400O IV 1401from Chianti

Density diagnostics in bombs: lower limit

Doppler shift relative to target line rest wavelength [km/s] spectral radiance [DN / pixel] O IV1399.77O IV1401.16Si IV1403.77

Si IV 1394O IV 1401 10no O IV linesupper limit:Si IV 1394O IV 1401> 700O IV1401.16Si IV1403.77

Density diagnostics in bombs: lower limitDoppler shift relative to target line rest wavelength [km/s] spectral radiance [DN / pixel] O IV1401.16Si IV1403.77

Si IV 1394O IV 1401> 700no O IV linesupper limit:

density @ Si IV origin: >5 x 1013 cm-3 @ Mg II origin: >3 x 1014 cm-3 comparable to density at T mimimumSummary of observations absorption lines (!) in EUV these line of neutral or singly ionized species have blueshifts of ~5 km/s cool layer above energy deposition event

still optically thin in Si IV bi-modal profile of Si IV (and C II, Mg II) strong bi-directional flow (supersonic, ~ Alfven-speed)

similar envelope of line profile in Mg II, C II, Si IV multi-thermal flow hosting plasma over a wide T range

flux cancellation below brightenings reconnection (consistent with flow speeds)

no O IV forbidden line emission with other evidence: source region in high-density plasma (probably not effect of non-Maxwellian e distribution; Dudik et al. 2014, ApJ 780, L12)

weak ( / no) signature in 171 and 304 bands overlying cool layer absorbs in He I and He II Lyman continuaScenario for the bombs

similar to EB scenario 1 inGeorgoulis et al (2002) ApJ 575, 5069Relation to Ellerman bombs ?

Ellerman bomb H-a unclear from observations, so far no H-a Ellerman bombs found at locations of these strange Si IV profiles (ongoing work, Vissers, G., Rouppe van der Voort et al, poster 4.21)

some of the Si IV bombs show also coronal counterpart

peaks of EB spectral profiles in H-a at different Doppler shifts than Si IV and Mg II in Si IV bombs

so far no enhancement in TR emission reported for EBs

energy estimations: Ellerman bombs: ~ 1028 ergs (Georgoulis et al. 2002; ApJ 575, 506) Si IV bombs: ~ 1029 ergs ~10 x EB

Yang et al. (2013) Sol. Phys. 288, 39 Si IV bombSi IVQSEBConclusions

Hot explosionsin the cool solar atmosphere

highlights importance of high spectral resolution (otherwise the absorption lines would not be visible)

energy release deep in the atmosphere (near/below T minimum)

overlying chromosphere is pushed upwards

huge amount of energy required to power flows and heat plasma

how is the chromospheric plasma heated to 100.000 K or even more?

3D MHD models predict only modest T increase (e.g. Archontis & Hood, 2009; A&A 508, 1469) 11thanksLine list

O IV lines and kappa-distributions

Dudk et al (2014, ApJ 780, L12)