| dc.description.abstract | Solar flares and coronal mass ejections (CMEs) are significant eruptions occurring in solar active regions and are generally believed to be caused by magnetic reconfiguration. However, these activities do not always occur simultaneously, so eruptions are categorized into eruptive flares, which are accompanied by CMEs, and confined flares, which are not, in this paper. Most research has focused on the magnetic properties to discuss the differences between the two types of flares. In this study, following the results of Imada et al. (2014) and Harra et al. (2009), the plasma characteristic changes in footpoints of active regions before the flare occurrences are targeted to the main purpose, which has been less discussed. To investigate both types of flares, imaging data from SDO/AIA and spectral data from Hinode/EIS, applying differential emission measure (DEM) analysis and spectral analysis, respectively, are utilized to discuss the Doppler velocity, non-thermal speed, and density of plasma in four footpoint regions within the active regions AR12473, associated with an M1.8 eruptive flare, and AR11158, associated with a C9.9 confined flare. The results suggest distinct pre-flare characteristics for the two flare events: before eruptive flares, there is a trend of increasing upward plasma flow velocity and non-thermal speed in the footpoints of the active region, along with a decrease in density; whereas before confined flares, the upward plasma flow velocity does not significantly increase and may even decrease, with a noticeable increase in density. To explain these findings, a possible scenario related to pre-flare active region evolution, such as coronal loop expansion, is proposed in this paper, aiming at a more complete understanding of solar eruptions. | en_US |