Suppression of Coronal Mass Ejections in Active Stars by an Overlying Large-scale Magnetic Field: A Numerical Study

Alvarado‐Gómez, Julián D.; Drake, J. J.; Cohen, Ofer; Moschou, S. P.; Garraffo, Cecilia

doi:10.3847/1538-4357/aacb7f

Cited by 147 publications

(136 citation statements)

References 102 publications

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“…No white-light flares are detected in the TESS light curve, but our evaluation of the flare amplitudes of Kepler superflare stars has shown that the possibility of occasional superflares on ι Hor cannot be excluded. Superflares would likely have strong effects on the early atmosphere of the Earth, especial if they yielded coronal mass ejections (but see Alvarado-Gómez et al 2018a, and references therein).…”

Section: Discussionmentioning

confidence: 99%

Multi-wavelength variability of the young solar analog ι Horologii

Sanz-Forcada

Stelzer

Coffaro

et al. 2019

A&A

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Context. Chromospheric activity cycles are common in late-type stars; however, only a handful of coronal activity cycles have been discovered. ι Hor is the most active and youngest star with known coronal cycles. It is also a young solar analog, and we are likely facing the earliest cycles in the evolution of solar-like stars, at an age (∼ 600 Myr) when life appeared on Earth. Aims. Our aim is to confirm the ∼1.6 yr coronal cycle and characterize its stability over time. We use X-ray observations of ι Hor to study the corona of a star representing the solar past through variability, thermal structure, and coronal abundances. Methods. We analyzed multi-wavelength observations of ι Hor using XMM-Newton, TESS, and HST data. We monitored ι Hor throughout almost seven years in X-rays and in two UV bands. The summed RGS and STIS spectra were used for a detailed thermal structure model, and the determination of coronal abundances. We studied rotation and flares in the TESS light curve. Results. We find a stable coronal cycle along four complete periods, more than covered in the Sun. There is no evidence for a second longer X-ray cycle. Coronal abundances are consistent with photospheric values, discarding any effects related to the first ionization potential. From the TESS light curve we derived the first photometric measurement of the rotation period (8.2 d). No flares were detected in the TESS light curve of ι Hor. We estimate the probability of having detected zero flares with TESS to be ∼ 2%. Conclusions. We corroborate the presence of an activity cycle of ∼1.6 yr in ι Hor in X-rays, more regular than its Ca ii H&K counterpart. A decoupling of the activity between the northern and southern hemispheres of the star might explain the disagreement. The inclination of the system would result in an irregular behavior in the chromospheric indicators. The more extended coronal material would be less sensitive to this effect.

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Section: Discussionmentioning

confidence: 99%

Multi-wavelength variability of the young solar analog ι Horologii

Sanz-Forcada

Stelzer

Coffaro

et al. 2019

A&A

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“…The recent direct detection of a stellar CME by Argiroffi et al (2019) follows the same trend. In Alvarado-Gómez et al (2018) we showed that these properties are expected due to the interaction between the escaping eruption and the suppressing effect imposed by the large-scale magnetic fields present in these stars.…”

Section: Introductionmentioning

confidence: 75%

Coronal Response to Magnetically Suppressed CME Events in M-dwarf Stars

Alvarado‐Gómez

Drake

Moschou

et al. 2019

ApJL

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We report the results of the first state-of-the-art numerical simulations of Coronal Mass Ejections (CMEs) taking place in realistic magnetic field configurations of moderately active M-dwarf stars. Our analysis indicates that a clear, novel, and observable, coronal response is generated due to the collapse of the eruption and its eventual release into the stellar wind. Escaping CME events, weakly suppressed by the large-scale field, induce a flare-like signature in the emission from coronal material at different temperatures due to compression and associated heating. Such flare-like profiles display a distinctive temporal evolution in their Doppler shift signal (from red to blue), as the eruption first collapses towards the star and then perturbs the ambient magnetized plasma on its way outwards. For stellar fields providing partial confinement, CME fragmentation takes place, leading to rise and fall flow patterns which resemble the solar coronal rain cycle. In strongly suppressed events, the response is better described as a gradual brightening, in which the failed CME is deposited in the form of a coronal rain cloud leading to a much slower rise in the ambient high-energy flux by relatively small factors (∼ 2 − 3). In all the considered cases (escaping/confined) a fractional decrease in the emission from mid-range coronal temperature plasma occurs, similar to the coronal dimming events observed on the Sun. Detection of the observational signatures of these CME-induced features requires a sensitive next generation X-ray space telescope.

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“…As noted by Drake et al (2013) a simple extrapolation from the relationship between solar CME kinetic energies and X-ray fluence leads to unphysically large energies for stellar CMEs. One possible solution is that the strong magnetic field in such stars may suppress the ejection of CMEs (even if a flare is observed) (Alvarado-Gómez et al 2018).…”

Section: Discussionmentioning

confidence: 99%

“…If this toroidal field extends beyond the surface into the corona, it may have a significant effect on the coronal structure and dynamics. Alvarado-Gómez et al (2018) suggest that it may act to enhance the confinement of coronal plasma, inhibiting the ejection of CMEs on very active stars. This may explain why the solar scaling of CME kinetic energy with X-ray flux cannot be extrapolated to active stars without requiring an unphysically large energy for stellar CMEs (Drake et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Slingshot prominences: coronal structure, mass loss and spin down

Jardine

Cameron

Donati

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The structure of a star's coronal magnetic field is a fundamental property that governs the high-energy emission from the hot coronal gas and the loss of mass and angular momentum in the stellar wind. It is, however, extremely difficult to measure. We report a new method to trace this structure in rapidly-rotating young convective stars, using the cool gas trapped on coronal field lines as markers. This gas forms "slingshot prominences" which appear as transient absorption features in H-α. By using different methods of extrapolating this field from the surface measurements, we determine locations for prominence support and produce synthetic H-α stacked spectra. The absorption features produced with a potential field extrapolation match well this those observed, while those from a non-potential field do not. In systems where the rotation and magnetic axes are well aligned, up to 50% of the prominence mass may transit the star and so produces a observable feature. This fraction may fall as low as 2% in very highly inclined systems. Ejected prominences carry away mass and angular momentum at rates that vary by two orders of magnitude, but which may approach those carried by the stellar wind.

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Suppression of Coronal Mass Ejections in Active Stars by an Overlying Large-scale Magnetic Field: A Numerical Study

Cited by 147 publications

References 102 publications

Multi-wavelength variability of the young solar analog ι Horologii

Multi-wavelength variability of the young solar analog ι Horologii

Coronal Response to Magnetically Suppressed CME Events in M-dwarf Stars

Slingshot prominences: coronal structure, mass loss and spin down

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