scholarly journals Observations of Magnetic Reconnection in the Transition Region of Quasi‐Parallel Shocks

2019 ◽  
Vol 46 (3) ◽  
pp. 1177-1184 ◽  
Author(s):  
I. Gingell ◽  
S. J. Schwartz ◽  
J. P. Eastwood ◽  
J. L Burch ◽  
R. E. Ergun ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Transition Region

scholarly journals Ellerman bombs and UV bursts: reconnection at different atmospheric layers

2020 ◽  
Vol 633 ◽  
pp. A58 ◽  
Author(s):  
Ada Ortiz ◽  
Viggo H. Hansteen ◽  
Daniel Nóbrega-Siverio ◽  
Luc Rouppe van der Voort
Keyword(s):  
Magnetic Flux ◽  
Magnetic Reconnection ◽  
Transition Region ◽  
Spatial Relationship ◽  
Spectral Lines ◽  
Near Ultraviolet ◽  
Temporal And Spatial ◽  
Imaging Spectrograph ◽  
High Cadence ◽  
Ellerman Bombs

The emergence of magnetic flux through the photosphere and into the outer solar atmosphere produces, amongst other dynamical phenomena, Ellerman bombs (EBs), which are observed in the wings of Hα and are due to magnetic reconnection in the photosphere below the chromospheric canopy. Signs of magnetic reconnection are also observed in other spectral lines, typical of the chromosphere or the transition region. An example are the ultraviolet (UV) bursts observed in the transition region lines of Si IV and the upper chromospheric lines of Mg II. In this work we analyze high-cadence, high-resolution coordinated observations between the Swedish 1m Solar Telescope (SST) and the Interface Region Imaging Spectrograph (IRIS) spacecraft. Hα images from the SST provide us with the positions, timings, and trajectories of EBs in an emerging flux region. Simultaneous, co-aligned IRIS slit-jaw images at 133 (C II, transition region), 140 (Si IV, transition region), and 279.6 (Mg II k, core, upper chromosphere) nm as well as spectroscopy in the far- and near-ultraviolet from the fast spectrograph raster allow us to study the possible chromospheric and transition region counterparts of those EBs. Our main goal is to study the possible temporal and spatial relationship between several reconnection events at different layers in the atmosphere (namely EBs and UV bursts), the timing history between them, and the connection of these dynamical phenomena to the ejection of surges in the chromosphere. We also investigate the properties of an extended UV burst and their variations across the burst domain. Our results suggest a scenario where simultaneous and co-spatial EBs and UV bursts are part of the same reconnection system occurring sequentially along a vertical or nearly vertical current sheet. Heating and bidirectional jets trace the location where reconnection takes place. These results support and expand those obtained from recent numerical simulations of magnetic flux emergence.

scholarly journals Mass and energy supply of a cool coronal loop near its apex

2018 ◽  
Vol 611 ◽  
pp. A49 ◽  
Author(s):  
Limei Yan ◽  
Hardi Peter ◽  
Jiansen He ◽  
Lidong Xia ◽  
Linghua Wang
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Magnetic Reconnection ◽  
Transition Region ◽  
Doppler Velocity ◽  
Small Scale ◽  
Solar Dynamics Observatory ◽  
Plasma Properties ◽  
Flux Tubes ◽  
Magnetic Flux Tubes

Context. Different models for the heating of solar corona assume or predict different locations of the energy input: concentrated at the footpoints, at the apex, or uniformly distributed. The brightening of a loop could be due to the increase in electron density ne, the temperature T, or a mixture of both.Aim. We investigate possible reasons for the brightening of a cool loop at transition region temperatures through imaging and spectral observation.Methods. We observed a loop with the Interface Region Imaging Spectrograph (IRIS) and used the slit-jaw images together with spectra taken at a fixed slit position to study the evolution of plasma properties in and below the loop. We used spectra of Si iv, which forms at around 80 000 K in equilibrium, to identify plasma motions and derive electron densities from the ratio of inter-combination lines of O IV. Additional observations from the Solar Dynamics Observatory (SDO) were employed to study the response at coronal temperatures (Atmospheric Imaging Assembly, AIA) and to investigate the surface magnetic field below the loop (Helioseismic and Magnetic Imager, HMI).Results. The loop first appears at transition region temperatures and later also at coronal temperatures, indicating a heating of the plasma in the loop. The appearance of hot plasma in the loop coincides with a possible accelerating upflow seen in Si IV, with the Doppler velocity shifting continuously from ~−70 km s−1 to ~−265 km s−1. The 3D magnetic field lines extrapolated from the HMI magnetogram indicate possible magnetic reconnection between small-scale magnetic flux tubes below or near the loop apex. At the same time, an additional intensity enhancement near the loop apex is visible in the IRIS slit-jaw images at 1400 Å. These observations suggest that the loop is probably heated by the interaction between the loop and the upflows, which are accelerated by the magnetic reconnection between small-scale magnetic flux tubes at lower altitudes. Before and after the possible heating phase, the intensity changes in the optically thin (Si IV) and optical thick line (C II) are mainly contributed by the density variation without significant heating.Conclusions. We therefore provide evidence for the heating of an envelope loop that is affected by accelerating upflows, which are probably launched by magnetic reconnection between small-scale magnetic flux tubes underneath the envelope loop. This study emphasizes that in the complex upper atmosphere of the Sun, the dynamics of the 3D coupled magnetic field and flow field plays a key role in thermalizing 1D structures such as coronal loops.

scholarly journals Observational Evidence of Magnetic Reconnection for Brightenings and Transition Region Arcades inIRISObservations

2017 ◽  
Vol 836 (1) ◽  
pp. 52 ◽  
Author(s):  
Jie Zhao ◽  
Brigitte Schmieder ◽  
Hui Li ◽  
Etienne Pariat ◽  
Xiaoshuai Zhu ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Transition Region ◽  
Observational Evidence

scholarly journals Solar Ultraviolet Bursts in the Joint Footpoints of Multiple Transition Region Loops

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1390
Author(s):  
Zhenyong Hou ◽  
Zhenghua Huang ◽  
Lidong Xia ◽  
Hui Fu ◽  
Youqian Qi ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Transition Region ◽  
Spectral Characteristics ◽  
Imaging Data ◽  
Flux Emergence ◽  
Physical Processes ◽  
Special Group ◽  
Space Images ◽  
Time Space ◽  
Solar Ultraviolet

Solar Ultraviolet bursts (UBs) associated with flux emergence are expected to help understand the physical processes of the flux emergence itself. In the present study, we analyse imaging and spectroscopic observations of a special group of UBs (including twelve of them) occurring in the joint footpoint regions of multiple transition region loops above the flux emerging regions. Consistent with previous studies of common UBs, we found that the spectral characteristics of this group of UBs are varied. Our results show that the responses of UBs in Ni ii, NUV continuum, Mg ii h and O i are originated from locations differ from that emits Si iv. The imaging data show that UBs have connections with the dynamics in the transition region loops. Brightenings starting from UB-regions and propagating along loops can be seen in SJ 1400/1330 Å and AIA 304 Å images and the corresponding time-space images. The apparent velocities are tens of kilometers per second in AIA 304 Å. For symmetry, the brightenings can propagate from the UB-regions towards opposite directions with similar apparent velocities in some cases. Given that these UBs are magnetic reconnection phenomena, we suggest that the propagating brightenings are the signals of the plasma flows resulted from heatings in the UB-regions.

scholarly journals Observational Evidence of Magnetic Reconnection in the Terrestrial Bow Shock Transition Region

2019 ◽  
Vol 46 (2) ◽  
pp. 562-570 ◽  
Author(s):  
Shan Wang ◽  
Li‐Jen Chen ◽  
Naoki Bessho ◽  
Michael Hesse ◽  
Lynn B. Wilson ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Transition Region ◽  
Observational Evidence ◽  
Bow Shock ◽  
Shock Transition

Effects of Ambipolar Diffusion on Prominence Thread Models

1994 ◽  
Vol 144 ◽  
pp. 315-321 ◽  
Author(s):  
M. G. Rovira ◽  
J. M. Fontenla ◽  
J.-C. Vial ◽  
P. Gouttebroze
Keyword(s):  
Energy Balance ◽  
Transition Region ◽  
Ambipolar Diffusion ◽  
Line Profiles ◽  
Balance Equations ◽  
Model Calculations ◽  
Partial Frequency ◽  
Frequency Redistribution ◽  
Partial Frequency Redistribution ◽  
Theoretical Structure

AbstractWe have improved previous model calculations of the prominence-corona transition region including the effect of the ambipolar diffusion in the statistical equilibrium and energy balance equations. We show its influence on the different parameters that characterize the resulting prominence theoretical structure. We take into account the effect of the partial frequency redistribution (PRD) in the line profiles and total intensities calculations.

A large rotating structure around AB Doradus A at VLBI scale

2019 ◽  
Vol 15 (S354) ◽  
pp. 189-194
Author(s):  
J. B. Climent ◽  
J. C. Guirado ◽  
R. Azulay ◽  
J. M. Marcaide
Keyword(s):  
Magnetic Reconnection ◽  
Main Sequence ◽  
Complex Structure ◽  
Main Sequence Star ◽  
Polar Cap ◽  
Vlbi Observations ◽  
Rotating Structure ◽  
Source Structure ◽  
Expected Position

AbstractWe report the results of three VLBI observations of the pre-main-sequence star AB Doradus A at 8.4 GHz. With almost three years between consecutive observations, we found a complex structure at the expected position of this star for all epochs. Maps at epochs 2007 and 2010 show a double core-halo morphology while the 2013 map reveals three emission peaks with separations between 5 and 18 stellar radii. Furthermore, all maps show a clear variation of the source structure within the observing time. We consider a number of hypothesis in order to explain such observations, mainly: magnetic reconnection in loops on the polar cap, a more general loop scenario and a close companion to AB Dor A.

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