Coronal flux ropes and their interplanetary counterparts

Gopalswamy, Ν.; Akiyama, S.; Yashiro, S.; Xie, H.

doi:10.1016/j.jastp.2017.06.004

Cited by 62 publications

(72 citation statements)

References 80 publications

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“…Substituting this value into the regression line (ΦRC = 0.79ΦAR 0.98 ), we get ΦRC ~2.9×10 23 Mx, suggesting that about 26% of the AR flux becoming reconnected in the eruption. Gopalswamy et al (2017b) also reported an empirical relation between ΦRC (in units of 10 21 Mx) and the CME kinetic energy (in units of 10 21 erg): KE = 0.19(ΦRC) 1.87 (2) For ΦRC = 2.9×10 23 Mx, this relation gives KE = 7.7×10 34 erg. This value is smaller by a factor of 5.5 than that (4.2×10 35 erg) derived from the scatter plot in Fig.…”

Section: Active Regions and Their Magnetic Fieldsmentioning

confidence: 94%

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Extreme Solar Eruptions and their Space Weather Consequences

Gopalswamy

2018

Extreme Events in Geospace

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Solar eruptions generally refer to coronal mass ejections (CMEs) and flares. Both are important sources of space weather. Solar flares cause sudden change in the ionization level in the ionosphere. CMEs cause solar energetic particle (SEP) events and geomagnetic storms. A flare with unusually high intensity and/or a CME with extremely high energy can be thought of examples of extreme events on the Sun. These events can also lead to extreme SEP events and/or geomagnetic storms. Ultimately, the energy that powers CMEs and flares are stored in magnetic regions on the Sun, known as active regions. Active regions with extraordinary size and magnetic field have the potential to produce extreme events. Based on current data sets, we estimate the sizes of one-in-hundred and one-in-thousand year events as an indicator of the extremeness of the events. We consider both the extremeness in the source of eruptions and in the consequences. We then compare the estimated 100-year and 1000-year sizes with the sizes of historical extreme events measured or inferred.

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Section: Active Regions and Their Magnetic Fieldsmentioning

confidence: 94%

“…The requirement of Bz = -78 nT to get a Dst value of -1160 nT is not unlikely. Gopalswamy et al (2017b) obtained an empirical relationship between the peak total magnetic field strength (Bt) and ICME speed: Bt = 0.06 VICME -13.58 nT (7) For VICME =2000 km/s, eq. (7) can be extrapolated to give Bt = 106 nT.…”

Section: Large Geomagnetic Stormsmentioning

confidence: 99%

Extreme Solar Eruptions and their Space Weather Consequences

Gopalswamy

2018

Extreme Events in Geospace

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“…The emission consists of a series of type III bursts, three episodes of type II bursts, and a flare continuum. Gopalswamy et al (2018d). A magnetic field of 4.4 G at 1.3 Rs corresponds to an axial field strength of ~75 mG at 10 Rs, assuming self-similar expansion of the flux rope.…”

Section: Radio Burstsmentioning

confidence: 99%

Source of Energetic Protons in the 2014 September 1 Sustained Gamma-ray Emission Event

et al. 2020

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We report on the source of >300 MeV protons during the SOL2014-09-01 sustained gamma-ray emission (SGRE) event based on multi-wavelength data from a wide array of space-and groundbased instruments. Based on the eruption geometry we provide concrete explanation for the spatially and temporally extended γ-ray emission from the eruption. We show that the associated flux rope is of low inclination (roughly oriented in the east-west direction), which enables the associated shock to extend to the frontside. We compare the centroid of the SGRE source with the location of the flux rope's leg to infer that the high-energy protons must be precipitating between the flux rope leg and the shock front. The durations of the SOL2014-09-01 SGRE event and the type II radio burst agree with the linear relationship between these parameters obtained for other SGRE events with duration ≥3 hrs. The fluence spectrum of the SEP event is very hard, indicating the presence of high-energy (GeV) particles in this event. This is further confirmed by the presence of an energetic coronal mass ejection (CME) with a speed >2000 km/s, similar to those in ground level enhancement (GLE) events. The type II radio burst had emission components from metric to kilometric wavelengths as in events associated with GLE events. All these factors indicate that the high-energy particles from the shock were in sufficient numbers needed for the production of γ-rays via neutral pion decay.

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“…This value is in the range of axial fields obtained for many coronal flux ropes obtained from the FRED technique (Gopalswamy et al 2017b,c), but well above the average (31.5 mG). For a set of 37 CME-ICME pairs, flux ropes were fit independently at the Sun (at 10 Rs using FRED) and at 1 AU (using in-situ observations) to get an empirical relation between the axial magnetic fields as (Gopalswamy et al 2017b):…”

Section: Reconnected Flux and 1-au Magnetic Field Strengthmentioning

confidence: 99%

Sun-to-earth propagation of the 2015 June 21 coronal mass ejection revealed by optical, EUV, and radio observations

Gopalswamy

Mäkelä

Akiyama

et al. 2018

Journal of Atmospheric and Solar-Terrestrial Physics

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We investigate the propagation of the 2015 June 21 CME-driven shock as revealed by the type II bursts at metric and longer wavelengths and coronagraph observations. The CME was associated with the second largest geomagnetic storm of solar cycle 24 and a large solar energetic particle (SEP) event. The eruption consisted of two M-class flares, with the first one being confined, with no metric or interplanetary radio bursts. However, there was intense microwave burst, indicating accelerated particles injected toward the Sun. The second flare was eruptive that resulted in a halo CME. The CME was deflected primarily by an equatorial coronal hole that resulted in the modification of the intensity profile of the associated SEP event and the duration of the CME at Earth. The interplanetary type II burst was particularly intense and was visible from the corona all the way to the vicinity of the Wind spacecraft with fundamental-harmonic structure. We computed the shock speed using the type II drift rates at various heliocentric distances and obtained information on the evolution of the shock that matched coronagraph observations near the Sun and in-situ observations near Earth. The depth of the geomagnetic storm is consistent with the 1-AU speed of the CME and the magnitude of the southward component.One of the controversies in this event is the low speed of the CME (~330 km s -1 ) in the outer corona (~26 solar radii) assumed by Piersanti et al. (2017), based on measurements provided by the CORIMP automatic CME catalog. With such low speed, these authors estimated the shock arrival at Earth on June 25, while the shock arrived on June 22, about 39.5 hours after the eruption. In fact, the shock and interplanetary (IP) CME (ICME) speeds were much higher at 1 AU (>700 km s -1 ). This is one of the motivations to clarify the CME kinematics near the Sun because we know that CMEs that survive into the IP medium to reach Earth are generally fast and wide (Gopalswamy et al. 2010a). We show that the shock speed is consistently high throughout the inner heliosphere and the deceleration is typical of most CMEs reported in the literature. We also use multiple methods to infer the true speed of the shock from white-light and radio data. In particular, we use IP type II radio burst data to derive the shock speed in the inner heliosphere. The CME and the shock are tightly coupled, so it is not possible to have a 330 km s -1 CME driving a >1000 km s -1 shock.The solar source of the CME has not received much attention in the literature (Liu et al. 2015;Piersanti et al. 2017). Soft-X-ray observations show two M-class flares in quick succession from the same active region. We examine the spatial distribution of the flare emission to show that it is different during the two flares: the first flare (X-ray class M2.0) was confined (no mass motion), while the second one (M2.6) was eruptive and hence associated with the CME in question.Another motivation stems from the confusion regarding the nature and extent of the IP counterpart of the 2015 Ju...

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Coronal flux ropes and their interplanetary counterparts

Cited by 62 publications

References 80 publications

Extreme Solar Eruptions and their Space Weather Consequences

Extreme Solar Eruptions and their Space Weather Consequences

Source of Energetic Protons in the 2014 September 1 Sustained Gamma-ray Emission Event

Sun-to-earth propagation of the 2015 June 21 coronal mass ejection revealed by optical, EUV, and radio observations

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