Spicules, the smallest observable jetlike dynamic features ubiquitous in the chromosphere, are supposedly an important potential source for small-scale solar wind transients, with supporting evidence yet needed. We studied the high-resolution H
- Award ID(s):
- 1821294
- NSF-PAR ID:
- 10141811
- Date Published:
- Journal Name:
- Science
- Volume:
- 366
- Issue:
- 6467
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- 890 to 894
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract α images (0.″10) and magnetograms (0.″29) from the Big Bear Solar Observatory to find that spicules are an ideal candidate for the solar wind magnetic switchbacks detected by the Parker Solar Probe (PSP). It is not that spicules are a miniature of coronal jets, but that they have unique properties not found in other solar candidates in explaining solar origin of switchbacks. (1) The spicules under this study originate from filigrees, all in a single magnetic polarity. Since filigrees are known as footpoints of open fields, the spicule guiding field lines can form a unipolar funnel, which is needed to create an SB patch, a group of field lines that switch from one common base polarity to the other polarity. (2) The spicules come in a cluster lined up along a supergranulation boundary, and the simulated waiting times from their spatial intervals exhibit a number distribution continuously decreasing from a few seconds to ∼30 minutes, similar to that of switchbacks. (3) From a time–distance map for spicules, we estimate their occurrence rate as 0.55 spicules Mm−2s−1, which is sufficiently high for detection by PSP. In addition, the dissimilarity of spicules with coronal jets, including the absence of base brightening and low correlation with EUV emission, is briefly discussed. -
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Aims. Recurring jets are observed in the solar atmosphere. They can erupt intermittently over a long period of time. By the observation of intermittent jets, we wish to understand what causes the characteristics of the periodic eruptions.Methods. We report intermittent jets observed by the Goode Solar Telescope (GST) with the TiO Broadband Filter Imager (BFI), the Visible Imaging Spectrometer (VIS) in Hα , and the Near-InfraRed Imaging Spectropolarimeter (NIRIS). The analysis was aided and complemented by 1400 Å and 2796 Å data from the Interface Region Imaging Spectrograph (IRIS). These observational instruments allowed us to analyze the temporal characteristics of the jet events. By constructing the Hα dopplergrams, we found that the plasma first moves upward, but during the second phase of the jet, the plasma flows back. Working with time slice diagrams, we investigated the characteristics of the jet dynamics.Results. The jet continued for up to 4 h. The time-distance diagram shows that the peak of the jet has clear periodic-eruption characteristics (5 min) during 18:00 UT–18:50 UT. We also found a periodic brightening phenomenon (5 min) during the jet bursts in the observed bands in the transition region (1400 Å and 2796 Å), which may be a response to intermittent jets in the upper solar atmosphere. The time lag is 3 min. Evolutionary images in the TiO band revealed a horizontal movement of the granulation at the location of the jet. By comparison to the quiet region of the Sun, we found that the footpoint of the jet is enhanced at the center of the Hα spectral line profile, without significant changes in the line wings. This suggests prolonged heating at the footpoint of the jet. In the mixed-polarity magnetic field region of the jet, we observed the emergence of magnetic flux, its cancellation, and shear, indicating possible intermittent magnetic reconnection. This is confirmed by the nonlinear force-free field model, which was reconstructed using the magneto-friction method.Conclusions. The multiwavelength analysis indicates that the events we studied were triggered by magnetic reconnection that was caused by mixed-polarity magnetic fields. We suggest that the horizontal motion of the granulation in the photosphere drives the magnetic reconnection, which is modulated byp -mode oscillations. -
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
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Abstract Plumes are bright structures in coronal holes extending from the solar surface into the corona and are considered as a possible source of the solar wind. Plumes are thought to be rooted in strong unipolar photospheric flux patches (network/plage region). The magnetic activities at the base of plumes may play a crucial role in producing outflows and propagating disturbances (PDs). However, the role of photospheric/chromospheric activities (e.g., jets/spicules) at the base of plumes and their connection to PDs is poorly understood. Using high-resolution observations of a plume taken on 2020 July 23 with the 1.6 m Goode Solar Telescope (GST), Interface Region Imaging Spectrograph (IRIS), and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we analyzed chromospheric/transition region activities at the base of the plume and their connection to outflows/PDs in the plume. The GST Visible Imaging Spectrometer images reveal repetitive spicules with blueshifted emission (pseudo-Doppler maps) at the plume’s footpoint. In addition, the photospheric magnetograms provide evidence of mixed polarities at the base of the plume. The IRIS Mg ii k Dopplergrams show strong blueshifted emission (∼50 km s −1 ) and a high brightness temperature (Mg ii k2 line) at the footpoint of the plume. The long-period PDs ( P ≈ 20–25 minutes) along the plume (AIA 171 Å) match the periodicity of spicules in the chromospheric images, suggesting a close connection between the spicules and the PDs. We suggest that the interchange reconnection between the closed and open flux of the coronal bright point at the plume’s footpoint is the most likely candidate to produce upflows and associated PDs along the plume.more » « less
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null (Ed.)Context. Spectroscopic observations of the emission lines formed in the solar transition region commonly show persistent downflows on the order of 10−15 km s −1 . The cause of such downflows, however, is still not fully clear and has remained a matter of debate. Aims. We aim to understand the cause of such downflows by studying the coronal and transition region responses to the recently reported chromospheric downflowing rapid redshifted excursions (RREs) and their impact on the heating of the solar atmosphere. Methods. We have used two sets of coordinated data from the Swedish 1 m Solar Telescope, the Interface Region Imaging Spectrograph, and the Solar Dynamics Observatory for analyzing the response of the downflowing RREs in the transition region and corona. To provide theoretical support, we use an already existing 2.5D magnetohydrodynamic simulation of spicules performed with the Bifrost code. Results. We find ample occurrences of downflowing RREs and show several examples of their spatio-temporal evolution, sampling multiple wavelength channels ranging from the cooler chromospheric to the hotter coronal channels. These downflowing features are thought to be likely associated with the returning components of the previously heated spicular plasma. Furthermore, the transition region Doppler shifts associated with them are close to the average redshifts observed in this region, which further implies that these flows could (partly) be responsible for the persistent downflows observed in the transition region. We also propose two mechanisms – (i) a typical upflow followed by a downflow and (ii) downflows along a loop –from the perspective of a numerical simulation that could explain the ubiquitous occurrence of such downflows. A detailed comparison between the synthetic and observed spectral characteristics reveals a distinctive match and further suggests an impact on the heating of the solar atmosphere. Conclusions. We present evidence that suggests that at least some of the downflowing RREs are the chromospheric counterparts of the transition region and lower coronal downflows.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/science.aaw2796
