scholarly journals Relationship between extreme ultraviolet microflares and small-scale magnetic fields in the quiet Sun

2015 ◽  
Vol 67 (3) ◽  
pp. 40 ◽  
Author(s):  
Fayu Jiang ◽  
Jun Zhang ◽  
Shuhong Yang
Keyword(s):  
Magnetic Fields ◽  
Extreme Ultraviolet ◽  
Small Scale ◽  
Quiet Sun

scholarly journals A small-scale EUV jet in the quiet Sun region

2012 ◽  
Vol 8 (S294) ◽  
pp. 555-559
Author(s):  
Junchao Hong ◽  
Yunchun Jiang ◽  
Ruisheng Zheng ◽  
Yi Bi
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Reconnection ◽  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Small Scale ◽  
Quiet Sun ◽  
Filament Channel ◽  
Field Lines ◽  
Using Data

AbstractSolar jets are typical proxies of small-scale magnetic reconnection events in the solar atmosphere. In this paper, we observe a small-scale jet in a solar quiet region, using data from SDO/Atmospheric Imaging Assembly (AIA), Helioseismic and Magnetic Imager (HMI), with supplemental data from STEREO/EUVI. From HMI magnetograms and calculated photospheric flows, we find that the jet is related to the interaction between unipolar network fields and emerging internetwork bipoles at the boundary of a supergranular cell. In AIA extreme-ultraviolet images, the jet actually includes two successive plasma ejections along different directions. The first ejection follows a distorted path which guides plasma into a small filament channel nearby. However, the second one shot straight along another direction that is parallel with extrapolated potential magnetic field lines on the local. According to these observations, we advocate that during the jet eruption new emerging magnetic fields are reconnecting at the edge of the supergranular cell with different kinds of ambient fields from low (magnetic canopy) to high (high-reaching loops) to allow the occurrence of successive ejections along different directions.

scholarly journals TURBULENT MAGNETIC FIELDS IN THE QUIET SUN: IMPLICATIONS OFHINODEOBSERVATIONS AND SMALL-SCALE DYNAMO SIMULATIONS

2009 ◽  
Vol 693 (2) ◽  
pp. 1728-1735 ◽  
Author(s):  
Jonathan Pietarila Graham ◽  
Sanja Danilovic ◽  
Manfred Schüssler
Keyword(s):  
Magnetic Fields ◽  
Small Scale ◽  
Quiet Sun

Transient small-scale brightenings in the quiet Sun corona: a model for "campfires" observed with Solar Orbiter

2021 ◽  
Author(s):  
Yajie Chen ◽  
Damien Przybylski ◽  
Hardi Peter ◽  
Hui Tian
Keyword(s):  
Convection Zone ◽  
Extreme Ultraviolet ◽  
Small Scale ◽  
Coronal Emission ◽  
Lower Corona ◽  
Quiet Sun ◽  
Self Consistent ◽  
Before And After ◽  
Field Lines ◽  
The Magnetic Field

<div> <div> <div> <p>Recent observations by the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter have revealed prevalent small-scale transient brightenings in the quiet solar corona termed campfires. To understand the generation mechanism of these coronal brightenings, we constructed a self- consistent and time-dependent quiet-Sun model extending from the upper convection zone to the lower corona using a realistic 3D radiation MHD simulation. From the model we have synthesized the coronal emission in the EUI 174 Å passband. We identified several transient coronal brightenings similar to those in EUI observations. The size and lifetime of these coronal brightenings are 2–4 Mm and ∼2 min, respectively. These brightenings are located at a height of 2–4 Mm above the photosphere, and the surrounding plasma is often heated above 1 MK. These findings are consistent with the observational characterisation of the campfires. Through a comparison of the magnetic field structures before and after the occurrence of brightenings, we conclude that these coronal brightenings are generated by component magnetic reconnection between interacting bundles of field lines or the relaxation of highly twisted flux ropes. Occurring in the coronal part of the atmosphere, these events show no measurable signature in the photosphere. These transient coronal brightenings may play an important role in heating of the local coronal plasma.</p> </div> </div> </div>

scholarly journals A persistent quiet-Sun small-scale tornado

2018 ◽  
Vol 618 ◽  
pp. A51 ◽  
Author(s):  
K. Tziotziou ◽  
G. Tsiropoula ◽  
I. Kontogiannis ◽  
E. Scullion ◽  
J. G. Doyle
Keyword(s):  
Vortex Flow ◽  
Extreme Ultraviolet ◽  
Spectral Lines ◽  
Small Scale ◽  
Large Radius ◽  
Vortex Flows ◽  
Line Profiles ◽  
Quiet Sun ◽  
Long Duration ◽  
Wide Range

Context. Vortex flows have been extensively observed over a wide range of spatial and temporal scales in different spectral lines, and thus layers of the solar atmosphere, and have been widely found in numerical simulations. However, signatures of vortex flows have only recently been reported in the wings of the Hα, but never so far in the Hα line centre. Aims. We investigate the appearance, characteristics, substructure, and dynamics of a 1.7 h persistent vortex flow observed from the ground and from space in a quiet-Sun region in several lines/channels covering all atmospheric layers from the photosphere up to the low corona. Methods. We use high spatial and temporal resolution CRisp Imaging SpectroPolarimeter (CRISP) observations in several wavelengths along the Hα and Ca II 8542 Å line profiles, simultaneous Atmospheric Imaging Assembly (AIA) observations in several Ultraviolet (UV) and Extreme ultraviolet (EUV) channels and Helioseismic and Magnetic Imager (HMI) magnetograms to study a persistent vortex flow located at the south solar hemisphere. Doppler velocities were derived from the Hα line profiles. Our analysis involves visual inspection and comparison of all available simultaneous/near-simultaneous observations and detailed investigation of the vortex appearance, characteristics and dynamics using time slices along linear and circular slits. Results. The most important characteristic of the analysed clockwise rotating vortex flow is its long duration (at least 1.7 h) and its large radius (~3″). The vortex flow shows different behaviours in the different wavelengths along the Hα and Ca II 8542 Å profiles reflecting the different formation heights and mechanisms of the two lines. Ground-based observations combined with AIA observations reveal the existence of a funnel-like structure expanding with height, possibly rotating rigidly or quasi-rigidly. However, there is no clear evidence that the flow is magnetically driven as no associated magnetic bright points have been observed in the photosphere. Hα and Ca II 8542 Å observations also reveal significant substructure within the flow, manifested as several individual intermittent chromospheric swirls with typical sizes and durations. They also exhibit a wide range of morphological patterns, appearing as dark absorbing features, associated mostly with mean upwards velocities around 3 km s−1 and up to 8 km s−1, and occupying on average ~25% of the total vortex area. The radial expansion of the spiral flow occurs with a mean velocity of ~3 km s−1, while its dynamics can be related to the dynamics of a clockwise rigidly rotating logarithmic spiral with a swinging motion that is, however, highly perturbed by nearby flows associated with fibril-like structures. A first rough estimate of the rotational period of the vortex falls in the range of 200–300 s. Conclusions. The vortex flow resembles a small-scale tornado in contrast to previously reported short-lived swirls and in analogy to persistent giant tornadoes. It is unclear whether the observed substructure is indeed due to the physical presence of individual intermittent, recurring swirls or a manifestation of wave-related instabilities within a large vortex flow. Moreover, we cannot conclusively demonstrate that the long duration of the observed vortex is the result of a central swirl acting as an “engine” for the vortex flow, although there is significant supporting evidence inferred from its dynamics. It also cannot be excluded that this persistent vortex results from the combined action of several individual smaller swirls further assisted by nearby flows or that this is a new case in the literature of a hydrodynamically driven vortex flow.

scholarly journals Small-Scale Magnetic Features Observed in the Photosphere

1990 ◽  
Vol 138 ◽  
pp. 129-146 ◽  
Author(s):  
Sara F. Martin
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Active Regions ◽  
Line Of Sight ◽  
Small Scale ◽  
Quiet Sun ◽  
Magnetic Features

Small-scale solar features identifiable on the quiet sun in magnetograms of the line-of-sight component consist of network, intranetwork, ephemeral region magnetic fields, and the elementary bipoles of ephemeral active regions. Network fields are frequently observed to split into smaller fragments and equally often, small fragments are observed to merge or coalesce into larger clumps; this splitting and merging is generally confined to the borders and vertices of the convection cells known as supergranules. Intranetwork magnetic fields originate near the centers of the supergranule convection cells and appear to increase in magnetic flux as they flow in approximate radial patterns towards the boundaries of the cells.

scholarly journals Origin of quiet-Sun magnetic fields revealed with Hinode

2012 ◽  
Vol 8 (S294) ◽  
pp. 143-148
Author(s):  
Ryohko Ishikawa
Keyword(s):  
Magnetic Fields ◽  
Spatial Scales ◽  
Small Scale ◽  
Quiet Sun ◽  
Convective Motions ◽  
Temporal And Spatial ◽  
The Relationship

AbstractQuiet-Sun magnetic fields are enigmatic in terms of their properties, and their origin is not well understood. One likely possibility is that they are a consequence of interactions with turbulent convective motions of various temporal and spatial scales. Here we investigate the relationship between small-scale magnetic fields and various convection flows. We demonstrate that in addition to granulation and supergranulation, mesogranulation also plays an important role in structuring quiet-Sun magnetic fields. We also study the vector magnetic fields in the quiet Sun, and propose that emerging granular-scale bipolar loops are major sources of the quiet-Sun magnetic fields.

scholarly journals Magnetic topology of the north solar pole

2018 ◽  
Vol 616 ◽  
pp. A46 ◽  
Author(s):  
A. Pastor Yabar ◽  
M. J. Martínez González ◽  
M. Collados
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Vector ◽  
Line Of Sight ◽  
Small Scale ◽  
Quiet Sun ◽  
The North ◽  
Field Distributions ◽  
Disc Centre ◽  
The Magnetic Field

The magnetism at the poles is similar to that of the quiet Sun in the sense that no active regions are present there. However, the polar quiet Sun is somewhat different from that at the activity belt as it has a global polarity that is clearly modulated by the solar cycle. We study the polar magnetism near an activity maximum when these regions change their polarity, from which it is expected that its magnetism should be less affected by the global field. To fully characterise the magnetic field vector, we use deep full Stokes polarimetric observations of the 15 648.5 and 15 652.8 Å FeI lines. We observe the north pole as well as a quiet region at disc centre to compare their field distributions. In order to calibrate the projection effects, we observe an additional quiet region at the east limb. We find that the two limb datasets share similar magnetic field vector distributions. This means that close to a maximum, the poles look like typical limb, quiet-Sun regions. However, the magnetic field distributions at the limbs are different from the distribution inferred at disc centre. At the limbs, we infer a new population of magnetic fields with relatively strong intensities (~600−800 G), inclined by ~30° with respect to the line of sight, and with an azimuth aligned with the solar disc radial direction. This line-of-sight orientation interpreted as a single magnetic field gives rise to non-vertical fields in the local reference frame and aligned towards disc centre. This peculiar topology is very unlikely for such strong fields according to theoretical considerations. We propose that this new population at the limbs is due to the observation of unresolved magnetic loops as seen close to the limb. These loops have typical granular sizes as measured in the disc centre. At the limbs, where the spatial resolution decreases, we observe them spatially unresolved, which explains the new population of magnetic fields that is inferred. This is the first (indirect) evidence of small-scale magnetic loops outside the disc centre and would imply that these small-scale structures are ubiquitous on the entire solar surface. This result has profound implications for the energetics not only of the photosphere, but also of the outer layers since these loops have been reported to reach the chromosphere and the low corona.

Two-dimensional power spectrum of small-scale magnetic fields on the quiet Sun

1991 ◽  
Vol 15 (2) ◽  
pp. 239
Author(s):  
Wang Jing-xiu ◽  
Shi Zhong-xian ◽  
Liu Jian-qiang
Keyword(s):  
Magnetic Fields ◽  
Power Spectrum ◽  
Small Scale ◽  
Two Dimensional ◽  
Quiet Sun
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