Multi thermal atmosphere of a mini solar flare during magnetic reconnection observed with IRIS

Abstract

The Interface Region Imaging Spectrograph(IRIS) with its high spatial and temporal resolution brings exceptional plasma diagnostics of solar chromospheric and coronal activity during magnetic reconnection. The aim of this work is to study the fine structure and dynamics of the plasma at a jet base forming a mini flare between two emerging magnetic fluxes (EMFs) observed with IRIS and the Solar Dynamics Observatory (SDO) instruments. We proceed to a spatio-temporal analysis of IRIS spectra observed in the spectral ranges of Mg II, C II, and Si IV ions. Doppler velocities from Mg II lines are computed by using a cloud model technique. Strong asymmetric Mg II and C II line profiles with extended blue wings observed at the reconnection site (jet base) are interpreted by the presence of two chromospheric temperature clouds, one explosive cloud with blueshifts at 290 km/s and one cloud with smaller Dopplershift (around 36 km/s). Simultaneously at the same location (jet base), strong emission of several transition region lines (e.g. O IV and Si IV), emission of the Mg II triplet lines of the Balmer-continuum and absorption of identified chromospheric lines in Si IV broad profiles have been observed and analysed. Such observations of IRIS line and continuum emissions allow us to propose a stratification model for the white-light mini flare atmosphere with multiple layers of different temperatures along the line of sight, in a reconnection current sheet. It is the first time that we could quantify the fast speed (possibly Alfvénic flows) of cool clouds ejected perpendicularly to the jet direction by using the cloud model technique. We conjecture that the ejected clouds come from plasma which was trapped between the two EMFs before reconnection or be caused by chromospheric-temperature (cool) upflow material like in a surge, during reconnection

arXiv comment20 pages, 17 figures, Accepted for publication in Astronomy & Astrophysics

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Cited by in corpus (13)

• Ultra-high-resolution Observations of Persistent Null-point Reconnection in the Solar Corona
• Solar jets observed with the Interface Region Imaging Spectrograph (IRIS)
• High-resolution observations of recurrent jets from an arch filament system
• Genesis and Coronal-jet-generating Eruption of a Solar Minifilament Captured by IRIS Slit-raster Spectra
• Solar surges related to UV bursts: Characterization through k-means, inversions and density diagnostics
• Plausibility of ultraviolet burst generation in the low solar chromosphere
• Interaction of solar jets with filaments: Triggering of large-amplitude filament oscillations
• Flare heating of the chromosphere: Observations of flare continuum from GREGOR and IRIS
• Spectroscopic investigations of a filament reconnecting with coronal loops during a two-ribbon solar flare
• Simulation of a Solar Jet Formed from an Untwisting Flux Rope Interacting with a Null Point
• Fan-shaped jet close to a light bridge
• Hard X-rays from the deep solar atmosphere. An unusual UV burst with flare properties
• Analysis of the Evolution of a Multi-Ribbon Flare and Failed Filament Eruption