Observational Kinematic Characteristics of Blobs in Solar Coronal Helmet and Pseudo Streamers

Abstract

Abstract We examine two helmet and two pseudo streamers (HSs and PSs) observed on 2018 and 2019. The HSs (PSs) have dark coronal cavities and stretched loop structures (twin coronal cavities and narrow plasma sheet) at their bases, which are well observed in K-Coronagraph (K-Cor). Their outer-corona structures (top of core, cusp, and stalk) are also clearly identified in LASCO-C2. By investigating LASCO-C2 images, we find the following characteristics. (1) Blobs persistently move outward along the centers of HSs and PSs as well as their legs until the base of a stalk. We also detect outward-moving blobs along their outsides. (2) Blobs along the HS centers formed below tops of cores (∼2.6 R ⊙), while the other HS and PS blobs might be generated below 2.0 R ⊙. (3) HS blob speeds are generally similar to or smaller than the solar wind speed based on Parker’s model, while PS ones are larger. (4) HS (PS) blob speeds along the streamer centers are slightly smaller (larger) than those along the streamer legs, might be explained by the expansion-factor model. The blob speeds inside streamer structures (centers and legs) are larger than outside ones closer to solar equator, similar to typical solar wind speed distributions at solar minimum. (5) Several blobs along the HS centers only show sudden speed jumps at streamer cusps. These might be caused by sunward tension forces of overlying stretched closed fields and/or bidirectional outflows by magnetic reconnections in the cusps.