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Observational study of chromospheric jets in and around a sunspot observed by NVST and SDO

Guotang Wu, Xiaoli Yan, Zhike Xue, Jincheng Wang, Zhe Xu, Liheng Yang, Yian Zhou, Liping Yang, Xinsheng Zhang, Qifan Dong, Zongyin Wu

TL;DR

This study compares two chromospheric jet populations in/around a sunspot using NVST H$eta$ observations and SDO data, identifying 50 inside-penumbra jets and 50 outside-penumbra jets. Kinematic analysis yields inside jets with $4$--$14$ km s$^{-1}$, $1$--$4$ Mm in length, $0.2$--$0.6$ Mm in width, and lifetimes of $135$--$450$ s, while outside jets reach $8$--$50$ km s$^{-1}$, extend up to $27$ Mm, have widths around $0.46$ Mm, and lifetimes of $135$--$630$ s, with mean values of $7.90$ km s$^{-1}$, $2.61$ Mm, $0.41$ Mm, $260$ s for inside jets and $19.04$ km s$^{-1}$, $6.26$ Mm, $0.46$ Mm, $327$ s for outside jets. Inside jets show brightenings in the H$eta$ blue wing in about $52 ext{ extpercent}$ of events, and outside jets are linked to magnetic flux emergence, opposite-polarity footpoints, and EUV brightenings, with some coronal counterparts indicating temperatures $>10^6$ K; both jet types are interpreted as driven by magnetic reconnection in distinct magnetic configurations. A DEM analysis reveals high-temperature components in some events, supporting reconnection-driven heating, and a rough thermal-energy estimate of $E_{ ext{thermal}} \\sim \\$ \frac{3}{2} n k T V$ per jet suggests these events contribute to atmospheric heating in the chromosphere and lower corona. Overall, the work provides a unified observational framework for penumbral microjets and chromospheric anemone jets within the same active region and clarifies their roles in solar atmosphere energetics.

Abstract

To better understand the characteristics, driving mechanisms, and potential heating contributions of chromospheric jets, we analyze two contrasting types: one originating from within the sunspot penumbra (inside jets), and the other originating from outside the penumbra (outside jets). Statistical analysis of 100 jets (50 inside jets and 50 outside jets) reveals that inside jets have a projected velocity range of 4--14~km\,s$^{-1}$, a length range of 1--4~Mm, a width range of 0.2--0.6~Mm, and a lifetime range of 135--450~s, with mean values of 7.90~km\,s$^{-1}$, 2.61~Mm, 0.41~Mm, and 260~s, respectively. About 52\% of inside jets are associated with brightenings in H$α$ blue wing images, and some show high-temperature signatures, suggesting a connection with localized energy release. In contrast, outside jets have higher velocities (8--50~km\,s$^{-1}$, average 19.04~km\,s$^{-1}$), greater lengths (average 6.26~Mm, up to 27.27~Mm), slightly larger widths (average 0.46~Mm), and longer lifetimes (135--630~s, average 327~s). They typically originate from regions of opposite magnetic polarities and are associated with magnetic flux emergence and EUV brightenings. Some outside jets correspond to coronal jets with inverted Y-shaped structures and temperatures exceeding one million Kelvin. Our results suggest that both jet types are driven by magnetic reconnection occurring in distinct magnetic field configurations and contribute to chromospheric and coronal heating.

Observational study of chromospheric jets in and around a sunspot observed by NVST and SDO

TL;DR

This study compares two chromospheric jet populations in/around a sunspot using NVST H observations and SDO data, identifying 50 inside-penumbra jets and 50 outside-penumbra jets. Kinematic analysis yields inside jets with -- km s, -- Mm in length, -- Mm in width, and lifetimes of -- s, while outside jets reach -- km s, extend up to Mm, have widths around Mm, and lifetimes of -- s, with mean values of km s, Mm, Mm, s for inside jets and km s, Mm, Mm, s for outside jets. Inside jets show brightenings in the H blue wing in about of events, and outside jets are linked to magnetic flux emergence, opposite-polarity footpoints, and EUV brightenings, with some coronal counterparts indicating temperatures K; both jet types are interpreted as driven by magnetic reconnection in distinct magnetic configurations. A DEM analysis reveals high-temperature components in some events, supporting reconnection-driven heating, and a rough thermal-energy estimate of \frac{3}{2} n k T V$ per jet suggests these events contribute to atmospheric heating in the chromosphere and lower corona. Overall, the work provides a unified observational framework for penumbral microjets and chromospheric anemone jets within the same active region and clarifies their roles in solar atmosphere energetics.

Abstract

To better understand the characteristics, driving mechanisms, and potential heating contributions of chromospheric jets, we analyze two contrasting types: one originating from within the sunspot penumbra (inside jets), and the other originating from outside the penumbra (outside jets). Statistical analysis of 100 jets (50 inside jets and 50 outside jets) reveals that inside jets have a projected velocity range of 4--14~km\,s, a length range of 1--4~Mm, a width range of 0.2--0.6~Mm, and a lifetime range of 135--450~s, with mean values of 7.90~km\,s, 2.61~Mm, 0.41~Mm, and 260~s, respectively. About 52\% of inside jets are associated with brightenings in H blue wing images, and some show high-temperature signatures, suggesting a connection with localized energy release. In contrast, outside jets have higher velocities (8--50~km\,s, average 19.04~km\,s), greater lengths (average 6.26~Mm, up to 27.27~Mm), slightly larger widths (average 0.46~Mm), and longer lifetimes (135--630~s, average 327~s). They typically originate from regions of opposite magnetic polarities and are associated with magnetic flux emergence and EUV brightenings. Some outside jets correspond to coronal jets with inverted Y-shaped structures and temperatures exceeding one million Kelvin. Our results suggest that both jet types are driven by magnetic reconnection occurring in distinct magnetic field configurations and contribute to chromospheric and coronal heating.

Paper Structure

This paper contains 9 sections, 11 figures.

Table of Contents

  1. Introduction
  2. Observations and data reduction
  3. Observations
  4. Data reduction methods
  5. Results
  6. Properties of inside jets
  7. Properties of outside jets
  8. Comparison between inside and outside jets
  9. Conclusions and discussion

Figures (11)

  • Figure 1: Overview of active region NOAA 13386. (a) H$\alpha$ line center image observed by NVST. The red and blue boxes outline subregions used in subsequent figures. (b) H$\alpha$ blue wing image at $-0.6\,\text{\AA}$. The black contours indicate brightenings where the intensity exceeds 140% of the mean value over the field of view. The yellow box outlines the subregion shown in Figure \ref{['fig:figure4']}. (c) Line-of-sight magnetogram from SDO/HMI, scaled from $-500$ G to $500$ G. Red lines represent 50 inside jets and blue lines represent 50 outside jets. The yellow and green boxes outline the subregions shown in Figures \ref{['fig:figure8']} and \ref{['fig:figure9']}, respectively. (d) Corresponding SDO/AIA 304 Å image. The sunspot umbra and penumbra contours shown in panels (a)--(d) are derived from the SDO/HMI continuum image, with the umbra marked in black and the penumbra in white.
  • Figure 2: Evolution of an inside jet. (a) Time sequence of H$\alpha$ line center images corresponding to the box A1 in Figure \ref{['fig:figure1']}(a). (b) Time sequence of H$\alpha$ blue wing images at $-0.6\,\text{\AA}$. Arrows in panels (a) and (b) indicate the top of the inside jet. (c) Enlarged view of the fourth image of panel (a). The red dashed line indicates the length of the inside jet, while the blue dashed line marks the position used to measure the width via intensity fitting. (d) Intensity profile along the blue dashed line in panel (c), with the dashed curve showing the observed data and the solid curve depicting the Gaussian profile. (e) Time-distance diagram obtained along the yellow dashed line in the second image of panel (b). The yellow dashed line in panel (e) is used to estimate the projected velocity, and the green annotation indicates the lifetime of the inside jet.
  • Figure 3: Statistical distributions of the physical properties of 50 inside jets. (a) Velocity distribution in km s$^{-1}$. (b) Length distribution in Mm. (c) Width distribution in Mm. (d) Lifetime distribution in 100 s. The yellow, red, blue, and green dashed lines in panels (a), (b), (c), and (d) indicate the mean values of the velocity, length, width, and lifetime, respectively. The mean value and sample standard deviation are annotated in each panel.
  • Figure 4: Brightenings identified in the H$\alpha$ blue wing at $-0.6\,\text{\AA}$ using a threshold of 140% of the mean intensity. (a) Enlarged view of the sunspot corresponding to the yellow box in Figure \ref{['fig:figure1']}(b). Three yellow boxes outline the subregions shown in panels (b)--(d). (b)--(d): Three examples of inside jets associated with brightenings. Yellow circles highlight the footpoints of the jets. (e)--(h): Histograms comparing the physical properties of inside jets associated with brightenings (red, 26 samples) and without brightenings (blue, 24 samples).
  • Figure 5: Multiwavelength observations of an inside jet corresponding to the box A2 in Figure \ref{['fig:figure1']}(a). The first row shows the H$\alpha$ line center images observed by NVST. The second row displays the corresponding H$\alpha$ blue wing images at $-0.6\,\text{\AA}$. The black contours in the first panel of the second row indicate brightenings identified using a threshold of 140% of the mean intensity. The third and fourth rows present observations from seven AIA EUV channels, arranged in order of increasing response temperature: $304\,\text{\AA}$, $171\,\text{\AA}$, $193\,\text{\AA}$, $211\,\text{\AA}$, $131\,\text{\AA}$, $335\,\text{\AA}$, and $94\,\text{\AA}$. The final panel shows the EM map integrated over the temperature range $\log T = 6.0$--$6.3$, derived from DEM analysis. Yellow circles highlight the footpoint of the inside jet, and blue arrows in some panels point to the two associated filaments.
  • ...and 6 more figures