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* News 04/04/20 * The archive is using a new backend database. This has thrown up a few SQL errors in the last few days. If you have any issues please email adavey@nso.edu with either the number of eprint you are trying to edit or a link to your preprint.

Investigation of pre-flare dynamics using the weighted horizontal magnetic gradient method: From small to major flare classes  

Marianna Korsos   Submitted: 2019-01-21 01:12

There is a wide range of eruptions in the solar atmosphere which contribute to space weather, including the major explosions of radiation known as flares. To examine pre-event behavior in delta-spot regions, we use here a method based on the weighted horizontal gradient of magnetic field (WG_M), defined between opposite polarity umbrae at the polarity inversion line of active regions (ARs) as measured using from the Debrecen Heliophysical Observatory catalogues. In this work, we extend the previous analysis of high-energy flares to include both medium (M) and low-energy (C and B) flares. First, we found a logarithmic relationship between the log value of highest flare class intensity (from B- to X-class) in a δ-spot AR and the maximum value of WG_M of the 127 ARs investigated. We confirm a trend in the convergence-divergence phase of the barycenters of opposite polarities in the vicinity of the polarity inversion line. The extended sample (i) affirms the linear connection between the durations of the convergence-divergence phases of barycenters of opposite polarities in delta-spot regions up to flare occurrence and (ii) provides a geometric constraint for the location of flare emission around the polarity inversion line. The method provides a tool to possibly estimate the likelihood of a subsequent flare of the same or larger energy.

Authors: Marianna B. Korsos, Shuhong Yang, Robert Erdelyi
Projects: None

Publication Status: accepted in JSWSC
Last Modified: 2019-01-22 16:08
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On flare predictability based on sunspot group evolution  

Marianna Korsos   Submitted: 2015-04-27 05:51

The forecast method introduced by Korsos et al.(2014) is generalised from the horizontal magnetic gradient (GM), defined between two opposite polarity spots, to all spots within an appropriately defined region close to the magnetic neutral line of an active region. This novel approach is not limited to searching for the largest GM of two single spots as in previous methods. Instead, the pre-flare conditions of the evolution of spot groups is captured by the introduction of the weighted horizontal magnetic gradient, or WGM. This new proxy enables the potential of forecasting flares stronger than M5. The improved capability includes (i) the prediction of flare onset time and (ii) an assessment whether a flare is followed by another event within about 18 hours. The prediction of onset time is found to be more accurate here. A linear relationship is established between the duration of converging motion and the time elapsed from the moment of closest position to that of the flare onset of opposite polarity spot groups. The other promising relationship is between the maximum of the WGM prior to flaring and the value of WGM at the moment of the initial flare onset in the case of multiple flaring. We found that when the WGM decreases by about 54%, then there is no second flare. If, however, when the WGM decreases less than 42%, then there will be likely a follow-up flare stronger than M5. This new capability may be useful for an automated flare prediction tool.

Authors: Marianna Korsos, Andras Ludmány, Robert Erdelyi, Tunde Baranyi
Projects: None

Publication Status: published
Last Modified: 2015-04-28 10:02
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PRE-FLARE DYNAMICS OF SUNSPOT GROUPS  

Marianna Korsos   Submitted: 2014-06-20 06:03

Several papers provide evidence that the most probable sites of flare onset are the regions of high horizontal magnetic field gradients in solar active regions. Besides the localization of flare-producing areas, this work intends to reveal the characteristic temporal variations in these regions prior to flares. This study uses sunspot data instead of magnetograms and follows the behavior of a suitable defined proxy measure representing the horizontal magnetic field gradient. The source of the data is the SDD (SOHO/MDI-Debrecen Data) sunspot catalog. The most promising pre-flare signatures are the following properties of gradient variation: (1) steep increase, (2) high maximum, (3) significant fluctuation, and (4) a gradual decrease between the maximum and the flare onset that can be related to the "pull mode" of the current layer. These properties may yield a tool for the assessment of flare probability and intensity within the following 8-10 hr.

Authors: M.B.Kors?s,T.Baranyi,A.Ludmány
Projects: SoHO-MDI

Publication Status: article published in Astrophysical Journal
Last Modified: 2014-06-20 06:31
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Investigation of pre-flare dynamics using the weighted horizontal magnetic gradient method: From small to major flare classes
On flare predictability based on sunspot group evolution
PRE-FLARE DYNAMICS OF SUNSPOT GROUPS

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