HOP 0479

abstract of observational proposal

Main Objective: Observations of solar polar plumes (and/or polar coronal structures) in X-rays, to supplement ground-based visible-light observations of the total solar eclipse of 2024 April 8 from the ground.

Scientific Justification: The coronal intensity in white light is a strong function of density alone, while the coronal intensity seen from Hinode/XRT is dependent on temperature and density. We want to know whether XRT-observed coronal features such as X-ray jets have a propensity to occur in the densest plumes (and/or polar coronal structures). We can address this by combining the ground-based and space-based observations during the eclipse. Our focus is on the study of coronal jets (e.g., Sterling et al. 2015, Nature, 523, 437), and their possible connection to plumes (e.g., Raouafi et al. 2008, ApJ, 682L, 137, Hanaoka et al. 2018, ApJ, 860, 142).

request to XRT

TARGET: First choice is a PCH. If no PCH is available, then target should be quiet-Sun polar region. If two PCHs are visible, then the one in which the hole is largest and/or best visible (“darkest” in EUV and X-ray images) should be selected.

TIMING: Request >~ 2 hours (longer if possible) on polar coronal hole (or polar quiet Sun) region, before and after totality. It is sufficient to have the observations within a few hours of totality (18:35 UT in Texas).

FIELD OF VIEW: 512x512 desired (384x384 acceptable) EXPOSURE TIME: Long exposure time (AEC setting = 2).

FILTERS: Al/poly and Al/mesh.

CADENCE: About 30 seconds between images would be acceptable.

CONTEXT IMAGES: In addition to the PCH images, it is vital to have full-Sun XRT images for context and alignment. These could be obtained with a typical XRT synoptic observation sequence, but as a minimum images in two filters, Al_poly and Al_mesh, are required. Two sets of images should be obtained, one prior to the ground-based eclipse, and another after the ground-based eclipse.

remarks

Dates: 2024 April 8

Time window: At least 2 hrs (ignoring eclipses observed from Hinode orbit) of PCH observations. Preferably one 2-hr+ block before totality and a second 2-hr+ block after totality. (Totality on the ground in Texas will be at ~18:35 UT, and at ~19:10 UT in Ohio.) In addition, two sets of XRT full-disk images should be taken for context in-between the two blocks. The sequences should be as close to totality as possible, but because plumes are persistent (lasting several hours), within a few hours of either side of totality is sufficient.

Target(s) of interest: Polar plumes, and jets around those plumes, are the target. Pointing should be at a polar coronal hole (PCH) region, similar to HOPs 339 and 376. If two PCHs are visible, select the one that is largest. If no PCHs are visible, then observe one of the polar regions.

Previous HOPs:
HOPs 339 and 376. Data from HOP 339 were used in Hanaoka et al. (2018, ApJ, 860, 142), and in Cho et al. (2021, ApJ, 909, 202).