Unified Relationship between Cold Plasma Ejections and Flare Energies Ranging from Solar Microflares to Giant Stellar Flares

Abstract

We often find spectral signatures of chromospheric cold plasma ejections accompanied by flares in a wide range of spatial scales in the solar and stellar atmospheres. However, the relationship between physical quantities (such as mass, kinetic energy, and velocity) of cold ejecta and flare energy has not been investigated in a unified manner for the entire range of flare energies to date. This study analyzed the spectra of cold plasma ejections associated with small-scale flares and solar flares (energy 1025–1029 erg) to supply smaller energy samples. We performed Hα imaging spectroscopy observation by the Solar Dynamics Doppler Imager on the Solar Magnetic Activity Research Telescope. We determined the physical quantities of the ejecta by cloud model fitting to the Hα spectrum. We determined the flare energy by differential emission measure analysis using the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory for small-scale flares and by estimating the bolometric energy for large-scale flares. As a result, we found that the ejection mass M and the total flare energy E tot follow a relation of M ∝ E tot 2 / 3 . We show that the scaling law derived from a simple physical model explains the solar and stellar observations with a coronal magnetic field strength as a free parameter. We also found that the kinetic energy and velocity of the ejecta correlate with the flare energy. These results suggest a common mechanism driven by magnetic fields to cause cold plasma ejections with flares on the Sun and stars.

Detection of a High-velocity Prominence Eruption Leading to a CME Associated with a Superflare on the RS CVn-type Star V1355 Orionis

“…Figure 8(a) indicates that the erupted prominence on V1355 Orionis has roughly the mass that expected from the scaling law of solar CMEs. This suggests that the prominence eruption on V1355 Orionis was caused by the same physical mechanism as the solar prominence eruptions/CMEs (e.g., Kotani et al 2023). Figure 8(a) also shows that it is the largest prominence eruption observed by blueshift.…”

Multiwavelength Campaign Observations of a Young Solar-type Star, EK Draconis. I. Discovery of Prominence Eruptions Associated with Superflares

“…, based on the assumption that the flare radiation energy E WL,bol ∼ 10 35 F GOES should be roughly less than CME kinetic energy Kotani et al (2023) suggested that the power-law index for the relation between erupted mass and flare energy scale is the same for CMEs and prominence eruptions, i.e., M F GOES 2 3 µ ; therefore, a similar scaling law for the upper limit of the prominence velociy V p can be also derived by following Takahashi et al (2016):…”

“…Our results suggest that, like solar CMEs/filament eruptions, the ejected mass against a given flare energy scale exhibits considerable scattering in the case of young Sun-like stars, spanning one to two orders of magnitude. Kotani et al 2023 theoretically suggested that the scattering may be explained by difference in magnetic field strength supporting the prominence. Hence, our findings in diversity in mass (and kinetic energy below) may be related to the diversity in the local magnetic field strength of the star.…”

“…Figure 22 shows the mass and kinetic energy as a function of flare-radiated energy for flares E1, E2, and E4 in comparison with solar filament eruptions/CMEs (Namekata et al 2022d;Kotani et al 2023) and their empirical scaling relations (Aarnio et al 2012;Drake et al 2013). Here, we focus comparisons among solar-type stars, the Sun and EK Dra, to show a solarstellar comparison without many different factors, such as surface gravity, atmospheric density, etc., while other studies have already focused on the comparison among different spectral types.…”

“…The original figures are taken from Namekata et al (2022d), and here we added two newly discovered stellar prominence eruptions on EK Dra in green-filled symbols. In addition, small-scale solar filament eruptions/surges investigated by Kotani et al (2023) were newly added for increasing samples in a small energy regime (10 28-30 erg ).…”