Slow and Fast MHD Shocks Associated with a Giant Cusp-Shaped Arcade on 1992 January 24

Shiota, Daikou; Yamamoto, T.; Sakajiri, Takuma; Isobe, Hiroaki; Chen, Pengfei; Shibata, Kazunari

doi:10.1093/pasj/55.3.l35

Cited by 11 publications

(14 citation statements)

References 27 publications

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“…Nitta (2004) considered the self-similar solution of Petschektype reconnection (i.e., with slow shocks) in free space and found that the reconnection rate is $0.05, nearly independent of the plasma-and, possibly, of the magnetic Reynolds number, too. It is also worth noting that signature of slow-mode MHD shocks associated with reconnection was found recently by X-ray observation of a giant arcade formation event (Shiota et al 2003).…”

Section: Introductionmentioning

confidence: 55%

Measurement of the Energy Release Rate and the Reconnection Rate in Solar Flares

Isobe

Takasaki

Shibata

2005

ApJ

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By using the method presented by Isobe et al., the nondimensional reconnection rate v in /v A has been determined for the impulsive phase of three two-ribbon flares, where v in is the velocity of the reconnection inflow and v A is the Alfvén velocity. The nondimensional reconnection rate is important to make a constraint on the theoretical models of magnetic reconnection. In order to reduce the uncertainty of the reconnection rate, it is important to determine the energy release rate of the flares from observational data as accurately as possible. To this end, we have carried out one-dimensional hydrodynamic simulations of a flare loop and synthesized the count rate detected by the Soft X-Ray Telescope (SXT) aboard the Yohkoh satellite. We found that the time derivative of the thermal energy contents in a flare arcade derived from SXT data is smaller than the real energy release rate by a factor of 0.3-0.8, depending on the loop length and the energy release rate. The results of the simulations are presented in the paper and used to calculate the reconnection rate. We found that the reconnection rate is 0.047 for the X2.3 flare on 2000 November 24, 0.015 for the M3.7 flare on 2000 July 14, and 0.071 for the C8.9 flare on 2000 November 16. These values are similar to that derived from the direct observation of the reconnection inflow by Yokoyama et al. and consistent with the fast reconnection models such as that of Petschek.

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Section: Introductionmentioning

confidence: 55%

Measurement of the Energy Release Rate and the Reconnection Rate in Solar Flares

Isobe

Takasaki

Shibata

2005

ApJ

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“…For the detailed observations of the flare, we have the chance to search for the signature of shocks associated with magnetic reconnection. Shiota et al (2003) once performed MHD simulations of a giant arcade formation with a model of magnetic reconnection coupled with heat conduction, and showed that the Y-shaped structure was identified to correspond to the slow and fast shocks associated with the magnetic reconnection. In this work, we study the physical parameters at the similar positions and similar times of the simulation of Shiota et al.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Observations of the Magnetic Reconnection Signature of an M2 Flare on 2000 March 23

Zhang

2009

ApJ

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Multi-wavelength observations of an M 2.0 flare event on 2000 March 23 in NOAA active region 8910 provide us a good chance to study the detailed structure and dynamics of the magnetic reconnection region. In the process of the flare, extreme ultraviolet (EUV) loops displayed two times of sideward motions upon a loop-top hard X-ray source with average velocities of 75 and 25.6 km s −1 , respectively. Meanwhile part of the loops disappeared and new post-flare loops formed. We consider these two motions to be the observational evidence of reconnection inflow, and find an X-shaped structure upon the post-flare loops during the period of the second motion. Two separations of the flare ribbons are associated with these two sideward motions, with average velocities of 3.3 and 1.3 km s −1 , separately. The sideward motions of the EUV loops and the separations of the flare ribbons are temporally consistent with two peaks of the X-ray flux. This indicates that there are two times of magnetic reconnection in the process of the flare. Using the observation of photospheric magnetic field, the velocities of the sideward motions and the separations, we deduce the corresponding coronal magnetic field strength to be about 13.2-15.2 G, and estimate the reconnection rates to be 0.05 and 0.02 for these two magnetic reconnection process, respectively. Besides the sideward motions of EUV loops and the separations of flare ribbons, we also observe motions of bright points upward and downward along the EUV loops with velocities ranging from 45.4 to 556.7 km s −1 , which are thought to be the plasmoids accelerated in the current sheet and ejected upward and downward when magnetic reconnection occurs and energy releases. A cloud of bright material flowing outward from the loop-top hard X-ray source with an average velocity of 51 km s −1 in the process of the flare may be accelerated by the tension force of the newly reconnected magnetic field lines. All the observations can be explained by schematic diagrams of magnetic reconnection.

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“…The cuspshaped loops and Y-shaped structure found by Soft X-ray Telescope aboard Yohkoh may be the reconnection slow shocks (Tsuneta et al 1992;Shiota et al 2003), but further evidence, e.g., jump in plasma density, pressure, and velocity, is obviously needed. Hinode/EIS will be a strong tool for this purpose Shiota et al 2004).…”

Section: How and Why Reconnection Is Fast?mentioning

confidence: 99%

Reconnection in solar flares: Outstanding questions

Isobe

Shibata

2009

J Astrophys Astron

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Space observations of solar flares such as those from Yohkoh, SOHO, TRACE, and RHESSI have revealed a lot of observational evidence of magnetic reconnection in solar flares: cusp-shaped arcades, reconnection inflows, plasmoids, etc. Thus it has been established, at least phenomenologically, that magnetic reconnection does occur in solar flares. However, a number of fundamental questions and puzzles still remain in the physics of reconnection in solar flares. In this paper, we discuss the recent progresses and future prospects in the study of magnetic reconnection in solar flares from both theoretical and observational points of view.

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Slow and Fast MHD Shocks Associated with a Giant Cusp-Shaped Arcade on 1992 January 24

Cited by 11 publications

References 27 publications

Measurement of the Energy Release Rate and the Reconnection Rate in Solar Flares

Measurement of the Energy Release Rate and the Reconnection Rate in Solar Flares

Observations of the Magnetic Reconnection Signature of an M2 Flare on 2000 March 23

Reconnection in solar flares: Outstanding questions

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