HOP 0508

abstract of observational proposal

Main Objective: Investigate the temporal evolution of coronal abundances during solar flares and their relationship to chromospheric wave activity

Scientific Justification: Elemental abundance variations in the solar corona are thought to result from the ponderomotive force of Alfven waves in the chromosphere, as described in Laming's FIP fractionation model (Laming 2012, 2015, 2017). This model predicts preferential transport of low-FIP ions depending on the wave energy and magnetic configuration of the lower atmosphere.

Recent observational studies have begun to test this model in active regions. Baker et al. (2021), Stangalini et al. (2021), and Testa et al. (2023) reported that wave and dynamic activity in the chromosphere and transition region are linked to coronal abundance variations. More recently, Lee et al. (2025) demonstrated a direct correlation between transverse MHD waves detected with GST/FISS and coronal FIP bias measured by Hinode/EIS, highlighting the value of coordinated high-resolution spectroscopic observations.

Following these studies, we propose to extend the investigation to solar flares, aiming to examine the temporal evolution of coronal abundances during flare onset and development, while simultaneously analyzing wave activity in the chromosphere and transition region. The flare targets will be selected based on Prof. Kusano's flare prediction model, known as the kappa scheme, which is based on the theory of double-arc instability (Kusano et al. 2020). This model identifies polarity inversion lines (PILs) as likely sites for flare initiation. We will focus on these regions and their surroundings, particularly compact strong magnetic patches near PILs, where inverse FIP effects have previously been reported (Doschek et al. 2015, Baker et al. 2019).

To capture both dynamic plasma behavior and abundance-sensitive emission, we will use Hinode/EIS in either high-cadence raster or sit-and-stare mode, depending on telemetry availability. Simultaneously, IRIS and GST/FISS will provide high-resolution diagnostics of wave and plasma dynamics from the chromosphere to the transition region.

This coordinated effort will help constrain wave-based fractionation mechanisms and improve our understanding of abundance changes associated with flare energy release.

References
- Baker, D., et al. 2019, ApJ, 875, 35
- Baker, D., et al. 2021, ApJ, 907, 16
- Doschek, G. A., et al. 2015, ApJL, 808, L7
- Kusano, K., et al. 2020, Science, 369, 587
- Laming, J. M. 2012, ApJ, 744, 115
- Laming, J. M. 2015, Living Reviews in Solar Physics, 12, 2
- Laming, J. M. 2017, ApJ, 844, 153 - Lee, K.-S., et al. 2025, A&A, 696, A189
- Stangalini, M., Baker, D., Valori, G., et al. 2021, Phil. Trans. R. Soc. A, 379, 20200216
- Testa, P., et al. 2023, ApJ, 944, 117

request to EIS

Hinode/EIS is the primary instrument for this proposal. We request a set of coordinated observations that includes a context image, a raster scan, and a flare-focused study. Depending on telemetry constraints, one of two flare observation options will be selected.

The requested EIS studies are as follows:
- Context: PRY_slot_contextLIQS (ID: 577), 1 run x 5 min
- Raster scan: HPW021VEL120x512v2_b (ID: 521), 1 run x 45 min
- Flare observation (Selected depending on telemetry constraints):
Option A: FlareResponse04 (ID: 650), 9 runs x ~6.6 min (~60 min total)
Option B: Sit-and-Stare: HPW021VEL001x512v2 (ID: 584), 1 run x 50 min

other participating instruments

IRIS requests:
We request IRIS coordination from June 27 - July 10, 2025, with daily observation windows from 16:30 UT to 21:30 UT. Two sets of OBSIDs are proposed depending on telemetry conditions.

June 27 - July 3
high telemetry - 3468103330 | Large sparse 8-step raster 7x120 8s C II Mg II h/k Deep x 0.5 Spati | 9.74 | 32.86 | 2.29 | 1.2+/-0.1 | 9.8+/-0.0 | 2.4+/-0.1 | 0.0+/-0.0 | 2.4+/-0.1 | 0.0+/-0.0 low telemetry - 3468103329 | Medium sparse 8-step raster 7x60 8s C II Mg II h/k Deep x 0.5 Spati | 9.73 | 14.96 | 1.05 | 1.2+/-0.1 | 9.7+/-0.0 | 2.4+/-0.1 | 0.0+/-0.0 | 2.4+/-0.1 | 0.0+/-0. Rolling desired to make the slit perpendicular to the PIL

July 4 - July 10
High telemetry - 3660103139 | Large sparse 16-step raster 15x120 16s C II Si IV Mg II h/k Deep | 25.61 | 55.41 | 1.47 | 1.6+/-0.1 | 25.6+/-0.0 | 12.8+/-0.1 | 12.8+/-0.1 | 12.8+/-0.1 | 0.0+/-0.0
Low telemetry - 3660103138 | Medium sparse 16-step raster 15x60 16s C II Si IV Mg II h/k Deep | 25.51 | 27.23 | 0.73 | 1.6+/-0.1 | 25.5+/-0.0 | 12.8+/-0.1 | 12.7+/-0.1 | 12.7+/-0.1 | 0.0+/-0.0

The OBSID can be adjusted if needed to accommodate planning constraints.

BBSO/GST - FISS, TiO, NIRIS

remarks

Dates: We request observations during the period of June 27 to July 10, 2025, to match the GST/FISS ground-based coordinated campaign. We would like to have at least 7 observing days during this period. While consecutive-day observations are not required, we prefer to continuously track the same active region if a highly flare-productive target is present.

Time window: The time window from 16:30 UT to 22:30 UT, which corresponds to the GST observing period, is preferred. The total duration of the requested EIS studies is approximately 2 hours per day. We request that the observations be scheduled within this time window while avoiding Hinode's night time during the eclipse season, ideally starting as early as possible after 16:30 UT.

Target(s) of interest: The primary target is a flare-productive active region, selected based on Prof. Kusano's kappa-scheme flare prediction model. We will focus on polarity inversion lines and nearby compact strong magnetic patches, which are considered favorable sites for flare initiation and abundance variation. This is not a ToO observation. Target selection will be coordinated with the GST/FISS campaign led by Dr. Kyoung-Sun Lee and Dr. Eun-Kyung Lim.

Previous HOPs:
HOP 420 - The HOP aimed to study the connection between coronal abundance and chromospheric wave activity using coordinated Hinode/EIS and GST/FISS observations. Although the joint campaign was affected by poor weather, a study using EIS and FISS data from an active region was completed and published as Lee et al. (2025), A&A, 696, A189