Measurement of magnetic field and relativistic electrons along a solar flare current sheet

Bin, Chen; Shen, Chengcai; Gary, Dale E.; Reeves, Katharine K.; Fleishman, G. D.; Yu, Sijie; Guo, Fan; Krucker, S.; Lin, Jin‐Ming; Nita, Gelu M.; Kong, Xiangliang

doi:10.1038/s41550-020-1147-7

Cited by 149 publications

(169 citation statements)

References 52 publications

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“…As reconnection proceeds, more small flux ropes are produced in the current sheet and flow up toward the erupting flux rope, or down toward the arcade. The solar flare of September 10, 2017, was observed by several instruments [32][33][34][35]. The gyrosynchrotron spectrum revealed relativistic electrons throughout the reconnecting current sheet, with an increase in intensity where the current sheet met the arcade.…”

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confidence: 99%

“…Our simulations reveal that the spectral index of nonthermal electrons and the number of the nonthermals depend strongly on the ambient guide field. Comparisons of MHD simulations of the September 10, 2017, flare with gyrosynchrotron emission of energetic electrons revealed that the guide field was 30% of the reconnecting magnetic field [34]. Based on the data from Fig.…”

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Electron Acceleration during Macroscale Magnetic Reconnection

et al. 2021

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The first self-consistent simulations of electron acceleration during magnetic reconnection in a macroscale system are presented. Consistent with solar flare observations, the spectra of energetic electrons take the form of power laws that extend more than two decades in energy. The drive mechanism for these nonthermal electrons is Fermi reflection in growing and merging magnetic flux ropes. A strong guide field suppresses the production of nonthermal electrons by weakening the Fermi drive mechanism. For a weak guide field the total energy content of nonthermal electrons dominates that of the hot thermal electrons even though their number density remains small. Our results are benchmarked with the hard x-ray, radio, and extreme ultraviolet observations of the X8.2-class solar flare on September 10, 2017.

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confidence: 99%

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Electron Acceleration during Macroscale Magnetic Reconnection

et al. 2021

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“…A more thorough analysis of the EOVSA data during the main phase of the event by Fleishman et al (2020) has provided the first maps of the dynamically decaying magnetic field strength in the cusp region of a flare. Additionally, the magnetic field vs. height along the reconnecting current sheet of the early, eruptive stage of the flare was measured and compared with an MHD simulation by Chen et al (2020).…”

Section: Gyrosynchrotron Emissionmentioning

confidence: 99%

Radio Measurements of the Magnetic Field in the Solar Chromosphere and the Corona

Alissandrakis

Gary

2021

Front. Astron. Space Sci.

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The structure of the upper solar atmosphere, on all observable scales, is intimately governed by the magnetic field. The same holds for a variety of solar phenomena that constitute solar activity, from tiny transient brightening to huge Coronal Mass Ejections. Due to inherent difficulties in measuring magnetic field effects on atoms (Zeeman and Hanle effects) in the corona, radio methods sensitive to electrons are of primary importance in obtaining quantitative information about its magnetic field. In this review we explore these methods and point out their advantages and limitations. After a brief presentation of the magneto-ionic theory of wave propagation in cold, collisionless plasmas, we discuss how the magnetic field affects the radio emission produced by incoherent emission mechanisms (free-free, gyroresonance, and gyrosynchrotron processes) and give examples of measurements of magnetic filed parameters in the quiet sun, active regions and radio CMEs. We proceed by discussing how the inversion of the sense of circular polarization can be used to measure the field above active regions. Subsequently we pass to coherent emission mechanisms and present results of measurements from fiber bursts, zebra patterns, and type II burst emission. We close this review with a discussion of the variation of the magnetic field, deduced by radio measurements, from the low corona up to ~ 10 solar radii and with some thoughts about future work.

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“…For Figure 1(b), we have selected an ∼8 GHz profile, because its peak time coincides with the peak time of the >100 MeV γ-ray emission observed by Fermi/ LAT. EOVSA's multifrequency MW images indicate that the ∼8 GHz emission concentrates at or near the bottom of the CME-trailing current sheet above the flare loops, in a magnetic bottle around the Y-type neutral point of magnetic field (the flare loops at a later instant of time are shown in Figure 2(a), and the main flare arcade 1 in (b); more MW images and analysis are given in Gary et al 2018;Chen et al 2020aChen et al , 2021.…”

Section: High-energy Event Morphology and Associationsmentioning

confidence: 99%

Multiple Sources of Solar High-energy Protons

Kocharov

Omodei

Mishev

et al. 2021

ApJ

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During the 24th solar cycle, the Fermi Large Area Telescope (LAT) has observed a total of 27 solar flares possessing delayed γ-ray emission, including the exceptionally well-observed flare and coronal mass ejection (CME) on 2017 September 10. Based on the Fermi/LAT data, we plot, for the first time, maps of possible sources of the delayed >100 MeV γ-ray emission of the 2017 September 10 event. The long-lasting γ-ray emission is localized under the CME core. The γ-ray spectrum exhibits intermittent changes in time, implying that more than one source of high-energy protons was formed during the flare-CME eruption. We find a good statistical correlation between the γ-ray fluences of the Fermi/LAT-observed delayed events and the products of corresponding CME speed and the square root of the soft X-ray flare magnitude. Data support the idea that both flares and CMEs jointly contribute to the production of subrelativistic and relativistic protons near the Sun.

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Measurement of magnetic field and relativistic electrons along a solar flare current sheet

Cited by 149 publications

References 52 publications

Electron Acceleration during Macroscale Magnetic Reconnection

Electron Acceleration during Macroscale Magnetic Reconnection

Radio Measurements of the Magnetic Field in the Solar Chromosphere and the Corona

Multiple Sources of Solar High-energy Protons

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