Near‐Sun speed of CMEs and the magnetic nonpotentiality of their source active regions

Tiwari, Sanjiv K.; Falconer, D. A.; Moore, Ronald L.; Venkatakrishnan, P.; Winebarger, Amy R.; Khazanov, Igor

doi:10.1002/2015gl064865

Cited by 12 publications

(10 citation statements)

References 70 publications

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“…The association between the 24-hour average values of the parameters and the linear speed of the CMEs is illustrated in Figure 8. These plots show basically what has been asserted in previous studies, namely that the maximum anticipated speed of a CME increases as the property value increases (Tiwari et al, 2015). For some properties (i.e.…”

Section: Mpil-related Parameters and Cme Kinematic Characteristicssupporting

confidence: 88%

“…This was showcased by Murray et al (2018) who combined CME detections and characteristics from the EU Framework Package 7 HELCATS project (www.helcats-fp7.eu) with active-region magnetic properties from the EU Horizon 2020 FLARECAST (flarecast.eu/) project. Although correlations tend to weaken in larger samples, general trends persist and, moreover, an upper limit on CME speeds may be imposed by magnetic non-potentiality parameters (Tiwari et al, 2015).…”

Section: Introductionmentioning

confidence: 98%

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Which Photospheric Characteristics Are Most Relevant to Active-Region Coronal Mass Ejections?

et al. 2019

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We investigate the relation between characteristics of coronal mass ejections and parameterizations of the eruptive capability of solar active regions widely used in solar flare prediction schemes. These parameters, some of which are explored for the first time, are properties related to topological features, namely, magnetic polarity inversion lines (MPILs) that indicate large amounts of stored non-potential (i.e. free) magnetic energy. We utilize the Space Weather Database of Notifications, Knowledge, Information (DONKI) and the Large Angle and Spectrometric Coronograph (LASCO) databases to find flare-associated coronal mass ejections and their kinematic characteristics while properties of MPILs are extracted from Helioseismic and Magnetic Imager (HMI) vector magnetic-field observations of active regions to extract the properties of sourceregion MPILs. The correlation between all properties and the characteristics of CMEs ranges from moderate to very strong. More significant correlations hold particularly for fast CMEs, which are most important in terms of adverse spaceweather manifestations. Non-neutralized currents and the length of the main I. KontogiannisMPIL exhibit significantly stronger correlations than the rest of the properties. This finding supports a causal relationship between coronal mass ejections and non-neutralized electric currents in highly sheared, conspicuous MPILs. In addition, non-neutralized currents and MPIL length carry distinct, independent information as to the eruptive potential of active regions. The combined total amount of non-neutralized electric currents and the length of the main polarity inversion line, therefore, reflect more efficiently than other parameters the eruptive capacity of solar active regions and the CME kinematic characteristics stemming from these regions.

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Section: Mpil-related Parameters and Cme Kinematic Characteristicssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 98%

Which Photospheric Characteristics Are Most Relevant to Active-Region Coronal Mass Ejections?

et al. 2019

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“…The study found that the highest-performing features, which characterise the non-potentiality of the magnetic field, are the mean horizontal gradient of the magnetic field and the twist parameter. A study by Tiwari et al (2015) found that active regions with a larger non-potentiality and total magnetic flux can produce both fast and slow CMEs, whereas smaller active regions with a more potential configuration can only produce slower CMEs. One key factor that plays a key role in CME productivity is the configuration of the overlying field (Török & Kliem 2005).…”

Section: Discussionmentioning

confidence: 99%

The Role of Flux Cancellation in Eruptions from Bipolar ARs

Yardley

Green

Driel‐Gesztelyi

et al. 2018

ApJ

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The physical processes or trigger mechanisms that lead to the eruption of coronal mass ejections (CMEs), the largest eruptive phenomenon in the heliosphere, are still undetermined. Low-altitude magnetic reconnection associated with flux cancellation appears to play an important role in CME occurrence as it can form an eruptive configuration and reduce the magnetic flux that contributes to the overlying, stabilising field. We conduct the first comprehensive study of 20 small bipolar active regions in order to probe the role of flux cancellation as an eruption trigger mechanism. We categorise eruptions from the bipolar regions into three types related to location and find that the type of eruption produced depends on the evolutionary stage of the active region. In addition we find that active regions that form eruptive structures by flux cancellation (low-altitude reconnection) had, on average, lower flux cancellation rates than the active region sample as a whole. Therefore, while flux cancellation plays a key role, by itself it is insufficient for the production of an eruption. The results support that although flux cancellation in a sheared arcade may be able to build an eruptive configuration, a successful eruption depends upon the removal of sufficient overlying and stabilising field. Convergence of the bipole polarities also appears to be present in regions that produce an eruption. These findings have important implications for understanding the physical processes that occur on our Sun in relation to CMEs and for space weather forecasting.

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“…Although in this Letter we present the method by applying it to the simplest-to-measure magnetic parameter of an AR, the total magnetic flux, the method is suitable for correcting the magnitude (absolute value) of any whole-AR magnetic parameter, e.g., the various size, twist and freeenergy proxies studied in Tiwari et al (2015) and Bobra and Couvidat (2015). Correcting freeenergy proxies out to 60 o from disk center is needed for improving forecasting of AR's CME/flare productivity.…”

Section: Discussionmentioning

confidence: 99%

A New Method to Quantify and Reduce the Net Projection Error in Whole-Solar-Active-Region Parameters Measured From Vector Magnetograms

Falconer

Tiwari

Moore

et al. 2016

ApJL

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Abstract:Projection error limits the use of vector magnetograms of active regions (ARs) far from disk center. In this Letter, for ARs observed up to 60 o from disk center, we demonstrate a method of measuring and reducing the projection error in the magnitude of any whole-AR parameter derived from a vector magnetogram that has been deprojected to disk center. The method assumes that the center-to-limb curve of the average of the parameter's absolute values measured from the disk passage of a large number of ARs and normalized to each AR's absolute value of the parameter at central meridian, gives the average fractional projection error at each radial distance from disk center. To demonstrate the method, we use a large set of large-flux ARs and apply the method to a whole-AR parameter that is among the simplest to measure: whole-AR magnetic flux. We measure 30,845 SDO/HMI vector magnetograms covering the disk passage of 272 large-flux ARs, each having whole-AR flux >10 22 Mx. We obtain the center-to-limb radial-distance run of the average projection error in measured whole-AR flux from a Chebyshev fit to the radial-distance plot of the 30,845 normalized measured values. The average projection error in the measured whole-AR flux of an AR at a given radial distance is removed by multiplying the measured flux by the correction factor given by the fit. The correction is important for both the study of evolution of ARs and for improving the accuracy of forecasting an AR's major flare/CME productivity.

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Near‐Sun speed of CMEs and the magnetic nonpotentiality of their source active regions

Cited by 12 publications

References 70 publications

Which Photospheric Characteristics Are Most Relevant to Active-Region Coronal Mass Ejections?

Which Photospheric Characteristics Are Most Relevant to Active-Region Coronal Mass Ejections?

The Role of Flux Cancellation in Eruptions from Bipolar ARs

A New Method to Quantify and Reduce the Net Projection Error in Whole-Solar-Active-Region Parameters Measured From Vector Magnetograms

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