CORONAL HEATING BY THE INTERACTION BETWEEN EMERGING ACTIVE REGIONS AND THE QUIET SUN OBSERVED BY THE SOLAR DYNAMICS OBSERVATORY

2015 ◽  
Vol 799 (2) ◽  
pp. L27 ◽  
Author(s):  
Jun Zhang ◽  
Bin Zhang ◽  
Ting Li ◽  
Shuhong Yang ◽  
Yuzong Zhang ◽  
...  
Keyword(s):  
Active Regions ◽  
Coronal Heating ◽  
Solar Dynamics Observatory ◽  
Quiet Sun ◽  
Solar Dynamics

scholarly journals Impulsive coronal heating during the interaction of surface magnetic fields in the lower solar atmosphere

2020 ◽  
Vol 644 ◽  
pp. A130
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
E. R. Priest ◽  
S. K. Solanki
Keyword(s):  
Solar Surface ◽  
Magnetic Energy ◽  
Active Regions ◽  
Opposite Polarity ◽  
Space Mission ◽  
Magnetic Polarity ◽  
Coronal Heating ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Solar Dynamics

Coronal plasma in the cores of solar active regions is impulsively heated to more than 5 MK. The nature and location of the magnetic energy source responsible for such impulsive heating is poorly understood. Using observations of seven active regions from the Solar Dynamics Observatory, we found that a majority of coronal loops hosting hot plasma have at least one footpoint rooted in regions of interacting mixed magnetic polarity at the solar surface. In cases when co-temporal observations from the Interface Region Imaging Spectrograph space mission are available, we found spectroscopic evidence for magnetic reconnection at the base of the hot coronal loops. Our analysis suggests that interactions of magnetic patches of opposite polarity at the solar surface and the associated energy release during reconnection are key to impulsive coronal heating.

scholarly journals Extreme-ultraviolet bursts and nanoflares in the quiet-Sun transition region and corona

2021 ◽  
Vol 647 ◽  
pp. A159
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
P. R. Young
Keyword(s):  
High Resolution ◽  
Solar Atmosphere ◽  
Significant Role ◽  
Extreme Ultraviolet ◽  
Coronal Heating ◽  
Solar Dynamics Observatory ◽  
Quiet Sun ◽  
Solar Dynamics ◽  
Event Based ◽  
Open Question

The quiet solar corona consists of myriads of loop-like features, with magnetic fields originating from network and internetwork regions on the solar surface. The continuous interaction between these different magnetic patches leads to transient brightenings or bursts that might contribute to the heating of the solar atmosphere. The literature on a variety of such burst phenomena in the solar atmosphere is rich. However, it remains unclear whether such transients, which are mostly observed in the extreme ultraviolet (EUV), play a significant role in atmospheric heating. We revisit the open question of these bursts as a prelude to the new high-resolution EUV imagery expected from the recently launched Solar Orbiter. We use EUV image sequences recorded by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) to investigate statistical properties of the bursts. We detect the bursts in the 171 Å filter images of AIA in an automated way through a pixel-wise analysis by imposing different intensity thresholds. By exploiting the high cadence (12 s) of the AIA observations, we find that the distribution of lifetimes of these events peaks at about 120 s. However, a significant number of events also have lifetimes shorter than 60 s. The sizes of the detected bursts are limited by the spatial resolution, which indicates that a larger number of events might be hidden in the AIA data. We estimate that about 100 new bursts appear per second on the whole Sun. The detected bursts have nanoflare-like energies of 1024 erg per event. Based on this, we estimate that at least 100 times more events of a similar nature would be required to account for the energy that is required to heat the corona. When AIA observations are considered alone, the EUV bursts discussed here therefore play no significant role in the coronal heating of the quiet Sun. If the coronal heating of the quiet Sun is mainly bursty, then the high-resolution EUV observations from Solar Orbiter may be able to reduce the deficit in the number of EUV bursts seen with SDO/AIA at least partly by detecting more such events.

scholarly journals Modelling nanoflares in active regions and implications for coronal heating mechanisms

2015 ◽  
Vol 373 (2042) ◽  
pp. 20140260 ◽  
Author(s):  
P. J. Cargill ◽  
H. P. Warren ◽  
S. J. Bradshaw
Keyword(s):  
Magnetic Field ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Coronal Heating ◽  
Cooling Time ◽  
Solar Dynamics Observatory ◽  
Solar Active Regions ◽  
Solar Dynamics

Recent observations from the Hinode and Solar Dynamics Observatory spacecraft have provided major advances in understanding the heating of solar active regions (ARs). For ARs comprising many magnetic strands or sub-loops heated by small, impulsive events (nanoflares), it is suggested that (i) the time between individual nanoflares in a magnetic strand is 500–2000 s, (ii) a weak ‘hot’ component (more than 10 6.6  K) is present, and (iii) nanoflare energies may be as low as a few 10 23 ergs. These imply small heating events in a stressed coronal magnetic field, where the time between individual nanoflares on a strand is of order the cooling time. Modelling suggests that the observed properties are incompatible with nanoflare models that require long energy build-up (over 10 s of thousands of seconds) and with steady heating.

scholarly journals Photospheric downflows observed with SDO/HMI, HINODE, and an MHD simulation

2021 ◽  
Vol 647 ◽  
pp. A178
Author(s):  
T. Roudier ◽  
M. Švanda ◽  
J. M. Malherbe ◽  
J. Ballot ◽  
D. Korda ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Surface ◽  
Outer Part ◽  
Data Cube ◽  
The Sun ◽  
Solar Dynamics Observatory ◽  
Mhd Simulation ◽  
Quiet Sun ◽  
Solar Dynamics ◽  
The Magnetic Field

Downflows on the solar surface are suspected to play a major role in the dynamics of the convection zone, at least in its outer part. We investigate the existence of the long-lasting downflows whose effects influence the interior of the Sun but also the outer layers. We study the sets of Dopplergrams and magnetograms observed with Solar Dynamics Observatory and Hinode spacecrafts and an magnetohydrodynamic (MHD) simulation. All of the aligned sequences, which were corrected from the satellite motions and tracked with the differential rotation, were used to detect the long-lasting downflows in the quiet-Sun at the disc centre. To learn about the structure of the flows below the solar surface, the time-distance local helioseismology was used. The inspection of the 3D data cube (x, y, t) of the 24 h Doppler sequence allowed us to detect 13 persistent downflows. Their lifetimes lie in the range between 3.5 and 20 h with a sizes between 2″ and 3″ and speeds between −0.25 and −0.72 km s−1. These persistent downflows are always filled with the magnetic field with an amplitude of up to 600 Gauss. The helioseismic inversion allows us to describe the persistent downflows and compare them to the other (non-persistent) downflows in the field of view. The persistent downflows seem to penetrate much deeper and, in the case of a well-formed vortex, the vorticity keeps its integrity to the depth of about 5 Mm. In the MHD simulation, only sub-arcsecond downflows are detected with no evidence of a vortex comparable in size to observations at the surface of the Sun. The long temporal sequences from the space-borne allows us to show the existence of long-persistent downflows together with the magnetic field. They penetrate inside the Sun but are also connected with the anchoring of coronal loops in the photosphere, indicating a link between downflows and the coronal activity. A links suggests that EUV cyclones over the quiet Sun could be an effective way to heat the corona.

scholarly journals Nature of the energy source powering solar coronal loops driven by nanoflares

2018 ◽  
Vol 615 ◽  
pp. L9 ◽  
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
S. K. Solanki
Keyword(s):  
Magnetic Field ◽  
Energy Source ◽  
Extreme Ultraviolet ◽  
Magnetic Energy ◽  
Plasma Heating ◽  
Active Regions ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Mixed Polarity ◽  
Solar Dynamics

Context. Magnetic energy is required to heat the corona, the outer atmosphere of the Sun, to millions of degrees. Aims. We study the nature of the magnetic energy source that is probably responsible for the brightening of coronal loops driven by nanoflares in the cores of solar active regions. Methods. We consider observations of two active regions (ARs), 11890 and 12234, in which nanoflares have been detected. To this end, we use ultraviolet (UV) and extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) for coronal loop diagnostics. These images are combined with the co-temporal line-of-sight magnetic field maps from the Helioseismic and Magnetic Imager (HMI) onboard SDO to investigate the connection between coronal loops and their magnetic roots in the photosphere. Results. The core of these ARs exhibit loop brightening in multiple EUV channels of AIA, particularly in its 9.4 nm filter. The HMI magnetic field maps reveal the presence of a complex mixed polarity magnetic field distribution at the base of these loops. We detect the cancellation of photospheric magnetic flux at these locations at a rate of about 1015 Mx s−1. The associated compact coronal brightenings directly above the cancelling magnetic features are indicative of plasma heating due to chromospheric magnetic reconnection. Conclusions. We suggest that the complex magnetic topology and the evolution of magnetic field, such as flux cancellation in the photosphere and the resulting chromospheric reconnection, can play an important role in energizing active region coronal loops driven by nanoflares. Our estimate of magnetic energy release during flux cancellation in the quiet Sun suggests that chromospheric reconnection can also power the quiet corona.

scholarly journals EMERGING DIMMINGS OF ACTIVE REGIONS OBSERVED BY THE SOLAR DYNAMICS OBSERVATORY

2012 ◽  
Vol 760 (2) ◽  
pp. L29 ◽  
Author(s):  
Jun Zhang ◽  
Shuhong Yang ◽  
Yang Liu ◽  
Xudong Sun
Keyword(s):  
Active Regions ◽  
Solar Dynamics Observatory ◽  
Solar Dynamics

scholarly journals Recurrent filament eruptions and associated CMEs

2013 ◽  
Vol 8 (S300) ◽  
pp. 489-490
Author(s):  
Brigitte Schmieder ◽  
Hebe Cremades ◽  
Cristina Mandrini ◽  
Pascal Démoulin ◽  
Yang Guo
Keyword(s):  
Magnetic Field ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Active Regions ◽  
The Other ◽  
Magnetic Configuration ◽  
Solar Dynamics Observatory ◽  
Solar Dynamics ◽  
Topology Computation ◽  
The Magnetic Field

AbstractWe investigate the violent events in the cluster of two active regions (ARs), NOAA numbers 11121 and 11123, observed on 11 November 2010 by the Solar Dynamics Observatory (SDO). Within one day the magnetic field intensity increased by 70% with the emergence of new groups of bipoles in AR 11123, where three filaments are seen along the complex inversion line. The destabilization of the filaments led to flares and CMEs. The CMEs around 08:24 UT and 17:00 UT are directly related to the partial eruption of one filament in the new AR, as shown by a topology computation and analysis. The other CMEs on this day are due to either other ARs or to the destabilization of the global magnetic configuration of the two ARs. This conclusion can be only reached by using the three eyes of SOHO, STEREO and SDO.

scholarly journals Self-cancellation of solar ephemeral regions observed by SDO

2012 ◽  
Vol 8 (S294) ◽  
pp. 159-160
Author(s):  
Shuhong Yang ◽  
Jun Zhang ◽  
Ting Li ◽  
Yang Liu
Keyword(s):  
Energy Release ◽  
Magnetic Energy ◽  
The Self ◽  
Solar Dynamics Observatory ◽  
Quiet Sun ◽  
Solar Dynamics ◽  
Magnetic Energy Release

AbstractWe study the ephemeral regions (ERs) in the quiet Sun observed by the Solar Dynamics Observatory, and find that they can be classified into two types: normal ERs (NERs) and self-cancelled ERs (SERs). We identify 2988 ERs among which there are 190 SERs, about 6.4% of the ERs. The total self-cancelled flux is 9.8% of the total ER flux. We suggest that the self-cancellation of SERs is caused by the submergence of magnetic loops connecting the dipolar patches, without magnetic energy release.

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