Evolutionary and flare-associated magnetic shear variations observed in a complex, flare-productive active region

Ambastha, Ashok; Hagyard, M. J.; West, E. A.

doi:10.1007/bf00645091

Cited by 76 publications

(48 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Observationally, since the first clear evidence from Yohkoh observations of Anwar et al (1993), rapid and irreversible changes in sunspot structure associated with flares have been studied for the past two decades. In the early time, most observations focused on the photospheric magnetic-field changes in the course of major flares, such as the magnetic shear changes along the flaring polarity inversion lines (PILs; Ambastha et al 1993;Chen et al 1994;Hagyard et al 1999), the stepwise changes in the longitudinal fields (Kosovichev & Zharkova 2001;Sudol & Harvey 2005), and so on. When these observations concluded that the longitudinal field flux variations were unbalanced between the disk-and limb-ward Wang et al 2002;Yurchyshyn et al 2004;Wang 2006), the white-light sunspot structure changes during major flares were also identified, which found that the penumbrae often became darker close to the central PILs while they decayed in the peripheral region Deng et al 2005;Liu et al 2005;Chen et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Rapid Penumbra and Lorentz Force Changes in an X1.0 Solar Flare

Jiang

Yang

et al. 2016

ApJL

View full text Add to dashboard Cite

We present observations of the violent changes in photospheric magnetic structures associated with an X1.1 flare, which occurred in a compact δ-configuration region in the following part of AR 11890 on 2013 November 8. In both central and peripheral penumbra regions of the small δ sunspot, these changes took place abruptly and permanently in the reverse direction during the flare: the inner/outer penumbra darkened/disappeared, where the magnetic fields became more horizontal/vertical. Particularly, the Lorentz force (LF) changes in the central/ peripheral region had a downward/upward and inward direction, meaning that the local pressure from the upper atmosphere was enhanced/released. It indicates that the LF changes might be responsible for the penumbra changes. These observations can be well explained as the photospheric response to the coronal field reconstruction within the framework of the magnetic implosion theory and the back reaction model of flares.

show abstract

Section: Introductionmentioning

confidence: 99%

Rapid Penumbra and Lorentz Force Changes in an X1.0 Solar Flare

Jiang

Yang

et al. 2016

ApJL

View full text Add to dashboard Cite

show abstract

“…Over a decade ago, the Big Bear Solar Observatory (BBSO) group discovered rapid and permanent changes of vector magnetic fields associated with flares (Wang et al 1992, but several other studies generated inconclusive results (Ambastha et al 1993;Hagyard et al 1999;Chen et al 1994;Li et al 2000aLi et al , 2000b. Kosovichev & Zharkova (2001) studied high-resolution Michelson Doppler Imager (MDI) magnetogram data for the 2000 July 14 ''Bastille Day Flare'' and found regions with a permanent decrease of the magnetic flux, which was related to the release of magnetic energy.…”

Section: Introductionmentioning

confidence: 99%

Rapid Changes of Photospheric Magnetic Fields around Flaring Magnetic Neutral Lines

Wang

2006

ApJ

View full text Add to dashboard Cite

In this paper we study the short-term evolution of magnetic fields associated with five flares in -sunspots. We concentrate on the analysis of the magnetic gradient along the flaring neutral lines (NLs). Obvious changes of the magnetic gradient occurred immediately and rapidly following the onset of each flare. A rapid gradient increase was found to be associated with three events, while a decrease was associated with the other two. The changes were permanent, and therefore not likely due to the flare emissions. In addition, we evaluated the mean relative motions between the two magnetic polarities in these -regions, in the directions parallel and perpendicular to the flaring NLs. We derived the mean positions of the two magnetic polarities using a center-of-mass (CoM) calculation and found that (1) converging motions correspond to a gradient increase and diverging motions, to a decrease; (2) for all the events, there appeared a sudden release of magnetic shear associated with each flare, signified by a decrease of CoM separation between 500 and 1200 km in the direction parallel to the NLs. Combining the findings presented here with those in previous papers, we propose that these results are evidence of magnetic reconnection at or close to the photosphere. When an active region is away from the solar disk center, the reconnected transverse fields cause an apparent increase of the flux in the polarity toward the limb and a decrease for the polarity closer to the disk center. This observational pattern was indeed found for all 10 available events that have been studied in the literature and in this paper. Finally, we offer some predictions for future observations when high-quality vector magnetogram sequences become available.

show abstract

“…Chen et al (1994) studied more than 20 M-class flares and determined that there was essentially no apparent change in magnetic fields associated with the flares. Studies conducted at the Marshall Space Flight Center (Ambastha et al 1993;Hagyard et al 1999) showed inconclusive results. The morphology of the photospheric magnetic field of an active region may or may not change as the result of a solar flare.…”

Section: Introductionmentioning

confidence: 99%

Rapid Penumbral Decay Associated with an X2.3 Flare in NOAA Active Region 9026

Deng

Liu

Guo

et al. 2005

ApJ

View full text Add to dashboard Cite

We present observations of rapid penumbral decay associated with a major flare in solar NOAA Active Region 9026 on 2000 June 6. Within 1.5 hr, an X2.3 flare accompanied by an 11 long filament eruption and a full-halo coronal mass ejection (CME) originated near the neutral line of a large -spot region, which was associated with significant changes in white-light structure and magnetic field topology: an increase of moving magnetic features (MMFs), flux emergence and cancellation, and, in particular, the rapid disappearance of two penumbral segments located in opposite-polarity regions on the north and south sides of the -spot. The rapid penumbral decay is believed to be the result of magnetic field topology change that was caused by rapid magnetic reconnection during the flare, rather than part of overall long-term evolution. We present a possible explanation of this event, using a ''magnetic breakout'' model for solar flares, considering its complex multipolar -configuration and associated filament eruption and CME, i.e., previously closed magnetic field lines opened up and reconnected at a null point above the neutral line of this -spot. The magnetic breakout caused an energy release from a highly sheared magnetic field in the umbrae and a transition of the magnetic arcades from low lying to high lying, which led to an increase of the inclination angle of the magnetic field lines in the peripheral penumbrae; i.e., the magnetic field turned from more inclined to more vertical and toward the inner umbrae. Once the magnetic field in the penumbrae was vertical enough, the Evershed flow ceased, the manifestation of which in white-light structure is the disappearance of peripheral penumbrae. We also discuss other possible flare models for this event and compare them in several observational features. The present observations provide further evidence that highly energetic events have a distinct associated photospheric magnetic field signature and support the findings of recent analyses of photospheric line-of-sight magnetograms from the Big Bear Solar Observatory (BBSO) and the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) that show rapid and permanent changes of photospheric magnetic fields associated with flares.

show abstract

Evolutionary and flare-associated magnetic shear variations observed in a complex, flare-productive active region

Cited by 76 publications

References 17 publications

Rapid Penumbra and Lorentz Force Changes in an X1.0 Solar Flare

Rapid Penumbra and Lorentz Force Changes in an X1.0 Solar Flare

Rapid Changes of Photospheric Magnetic Fields around Flaring Magnetic Neutral Lines

Rapid Penumbral Decay Associated with an X2.3 Flare in NOAA Active Region 9026

Contact Info

Product

Resources

About