skip to main content

Explore Research Products in the NSF-PAR

Title: Quasiperiodic Microjets Driven by Granular Advection as Observed With High-resolution Imaging at He i 10830 Å
Abstract With high-resolution narrowband He i 10830 Å filtergrams from Goode Solar Telescope, we give an extensive analysis for four granule-sized microeruptions which appear as the gentle ejection of material in He i 10830 Å band. The analysis was aided with the EUV data from Atmospheric Imaging Assembly and line-of-sight magnetograms from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. The microeruptions are situated on magnetic polarity inversion lines (PILs), and their roots are accurately traced down to intergranular lanes. Their durations are different: two microeruptions are repetitive microjets, lasting ∼50 and 27 minutes respectively, while the other two events are singular, lasting ∼5 minutes. For the two microjets, they are continuous and recurrent in the He i 10830 Å band, and the recurrence is quasiperiodic with a period of ∼5 minutes. We found that only transient cospatial EUV brightenings are observed for the longer duration microjets and EUV brightenings are absent for the two singular microeruptions. What is essential to the longer duration microjets is that granules with the concentration of a positive magnetic field persistently transport the magnetic field to the PILs, canceling the opposite magnetic flux and making the base of the two microjets and the underlying granules migrate with the speed of ∼0.25 and 1.0 km s −1 . The observations support the scenario of magnetic reconnection for the quasiperiodic microjets and further show that the reconnection continuously generates multitemperature components, especially the cool component with chromospheric temperature. In addition, the ongoing reconnection is modulated by p-mode oscillations inside the Sun.  more » « less
Award ID(s):
1821294
NSF-PAR ID:
10384298
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
928
Issue:
2
ISSN:
0004-637X
Page Range / eLocation ID:
153
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ( , Research in Astronomy and Astrophysics)
    Abstract In this paper, we report the observed temporal correlation between extreme-ultraviolet (EUV) emission and magneto-acoustic oscillations in an EUV moss region, which is the footpoint region only connected by magnetic loops with million-degree plasma. The result is obtained from a detailed multi-wavelength data analysis of the region with the purpose of resolving fine-scale mass and energy flows that come from the photosphere, pass through the chromosphere and finally heat the solar transition region or the corona. The data set covers three atmospheric levels on the Sun, consisting of high-resolution broad-band imaging at TiO 7057 Å and the line of sight magnetograms for the photosphere, high-resolution narrow-band images at helium i 10830 Å for the chromosphere and EUV images at 171 Å for the corona. The 10830 Å narrow-band images and the TiO 7057 Å broad-band images are from a much earlier observation on 2012 July 22 with the 1.6 meter aperture Goode Solar Telescope (GST) at Big Bear Solar Observatory (BBSO) and the EUV 171 Å images and the magnetograms are from observations made by Atmospheric Imaging Assembly (AIA) or Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We report the following new phenomena: (1) Repeated injections of chromospheric material appearing as 10830 Å absorption are squirted out from inter-granular lanes with a period of ∼ 5 minutes. (2) EUV emissions are found to be periodically modulated with similar periods of ∼ 5 minutes. (3) Around the injection area where 10830 Å absorption is enhanced, both EUV emissions and strength of the magnetic field are remarkably stronger. (4) The peaks on the time profile of the EUV emissions are found to be in sync with oscillatory peaks of the stronger magnetic field in the region. These findings may give a series of strong evidences supporting the scenario that coronal heating is powered by magneto-acoustic waves. 
    more » « less
  2. ; ; ( , The Astrophysical Journal)
    Abstract Solar jets are ubiquitous phenomena in the solar atmosphere. They are important in mass and energy transport to the upper atmosphere and interplanetary space. Here, we report a detailed analysis of a small-scale chromospheric jet with high-resolution He i 10830 Å and TiO 7057 Å images observed by the 1.6 m aperture Goode Solar Telescope at the Big Bear Solar Observatory. The observation reveals the finest dark threads inside the jet are rooted in the intergranular lanes. Their width is equal to the telescope’s diffraction limit at 10830 Å (∼100 km). The jet is recurrent and its association with the emergence and convergence of magnetic flux is observed. Together with other important features like photospheric flow toward the magnetic polarity inversion line, a bald-patch magnetic configuration, and earlier excitation of helium atoms, we propose that the jet might be initiated by magnetic reconnection in a U-shaped loop configuration. The plasmoid configuration results from the possible buoyancy of the magnetic reconnection, which reoccurs in a second step with an overlying magnetic field line. Notably, the second-step magnetic reconnection produces not only bidirectional cool or hot flows but also a new U-shaped loop configuration. The feature may be used to explain the recurrent behavior of the jet, since the new U-shaped loop can be driven to reconnect again. 
    more » « less
  3. ; ; ; ; ; ; ( , Research in Astronomy and Astrophysics)
    Abstract We gave an extensive study for the quasi-periodic perturbations on the time profiles of the line of sight (LOS) magnetic field in 10 × 10 sub-areas in a solar plage region (corresponds to a facula on the photosphere). The perturbations are found to be associated with the enhancement of He I 10830 Å absorption in a moss region, which is connected to loops with million-degree plasma. FFT analysis to the perturbations gives a kind of spectrum similar to that of Doppler velocity: a number of discrete periods around 5 minutes. The amplitudes of the magnetic perturbations are found to be proportional to magnetic field strength over these sub-areas. In addition, magnetic perturbations lag behind a quarter of the cycle in the phase with respect to the p-mode Doppler velocity. We show that the relationships can be well explained with an MHD solution for the magneto-acoustic oscillations in high- β plasma. Observational analysis also shows that, for the two regions with the stronger and weaker magnetic field, the perturbations are always anti-phased. All findings show that the magnetic perturbations are actually magneto-acoustic oscillations on the solar surface, the photosphere, powered by p-mode oscillations. The findings may provide a new diagnostic tool for exploring the relationship between magneto-acoustic oscillations and the heating of the solar upper atmosphere, as well as their role in helioseismology. 
    more » « less
  4. ; ; ; ; ; ; ; ( , The Astrophysical Journal)
    Abstract

    Solar filaments exist as stable structures for extended periods of time before many of them form the core of a coronal mass ejection (CME). We examine the properties of an erupting filament on 2017 May 29–30 with high-resolution Hei10830 Å and Hαspectra from the Dunn Solar Telescope, full-disk Dopplergrams of Hei10830 Å from the Chromospheric Telescope, and EUV and coronograph data from SDO and STEREO. Pre-eruption line-of-sight velocities from an inversion of Heiwith the HAZEL code exhibit coherent patches of 5 Mm extent that indicate counter-streaming and/or buoyant behavior. During the eruption, individual, aligned threads appear in the Heivelocity maps. The distribution of velocities evolves from Gaussian to strongly asymmetric. The maximal optical depth of Hei10830 Å decreased fromτ= 1.75 to 0.25, the temperature increased by 13 kK, and the average speed and width of the filament increased from 0 to 25 km s−1and 10 to 20 Mm, respectively. All data sources agree that the filament rose with an exponential acceleration reaching 7.4 m s−2that increased to a final velocity of 430 km s−1at 22:24 UT; a CME was associated with this filament eruption. The properties during the eruption favor a kink/torus instability, which requires the existence of a flux rope. We conclude that full-disk chromospheric Dopplergrams can be used to trace the initial phase of on-disk filament eruptions in real time, which might potentially be useful for modeling the source of any subsequent CMEs.

     
    more » « less
  5. ; ; ; ; ; ; ( , The Astrophysical Journal)
    Abstract While solar flares are predominantly characterized by an intense broadband enhancement to the solar radiative output, certain spectral lines and continua will, in theory, exhibit flare-induced dimmings. Observations of transitions of orthohelium He i λ λ 10830 Å and the He i D3 lines have shown evidence of such dimming, usually followed by enhanced emission. It has been suggested that nonthermal collisional ionization of helium by an electron beam, followed by recombinations to orthohelium, is responsible for overpopulating those levels, leading to stronger absorption. However, it has not been possible observationally to preclude the possibility of overpopulating orthohelium via enhanced photoionization of He i by EUV irradiance from the flaring corona followed by recombinations. Here we present radiation hydrodynamics simulations of nonthermal electron-beam-driven flares where (1) both nonthermal collisional ionization of helium and coronal irradiance are included, and (2) only coronal irradiance is included. A grid of simulations covering a range of total energies deposited by the electron beam and a range of nonthermal electron-beam low-energy cutoff values were simulated. In order to obtain flare-induced dimming of the He i 10830 Å line, it was necessary for nonthermal collisional ionization to be present. The effect was more prominent in flares with larger low-energy cutoff values and longer lived in weaker flares and flares with a more gradual energy deposition timescale. These results demonstrate the usefulness of orthohelium line emission as a diagnostic of flare energy transport. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email