Research Highlights

Coronal mass ejections (CMEs) are large eruptions of plasma from the Sun that can affect space weather near Earth. Coronagraphs observe these eruptions by measuring sunlight scattered by electrons in the solar corona and heliosphere. However, these images are two-dimensional projections of a three-dimensional structure, which makes it difficult to determine the true shape, density, and motion of a CME. We introduce SuNeRF-CME, a new method for reconstructing the three-dimensional plasma structure of CMEs from coronagraph images taken from multiple viewpoints.

The large-scale traveling ionospheric disturbances (LSTIDs) over the Asian-Pacific sector during the 10-11 May 2024 superstorm are investigated using ionosonde observation and simulation from a whole geospace model - Multiscale Atmosphere Geospace Environment (MAGE), which fully couples multiple magnetosphere, ionosphere and thermosphere models.

Solar physicists use instruments called polarimeters to measure the polarization of sunlight, which reveals the strength and structure of the Sun's magnetic field. Before a polarimeter can deliver reliable measurements, it must be calibrated by feeding known polarization states into the instrument. Calibration takes time, and telescope time is precious — particularly for solar telescopes, where intense sunlight limits how long calibration optics can safely remain in the beam. This raises a key question: what sequence of calibration measurements yields the most accurate result in a given amount of time?

A balloon-borne instrument called HIWIND was launched from New Zealand to observe thermospheric winds in the mid-latitudes. The observed winds were compared with TIEGCM model simulation and were found to be much larger than the simulated results.

D. Afonso Delgado addresses the need to model the effects of radiation anisotropy and atomic coherence on the Stokes profiles
of magnetically-sensitive lines formed in the solar chromosphere. Accounting for the physics of scattering polarization associated with these effects, and how they map to the strength and direction of weak magnetic fields on the Sun is a formidable computational task when done fully self-consistently. This has hindered the broad heliophysics community from gaining prompt access to reliable data products from solar facility spectro-polarimeters concerning quiet-Sun magnetism.

Authors R. Casini, D. Harrington, and A. de Wijn review the algebraic definition of the efficiency of a polarization modulation scheme, which is commonly adopted for solar and stellar spectro-polarimetry applications, and generalize it to allow distinct states of the modulation cycle to have arbitrary throughput and different photon-noise statistics for each state.

D. Aggarwal, S. Kumar, B. C. Martinez, N. M. Pedatella, X. Lu, and J. Oberheide examine how a major SSW in 2020-2021 affected global atmospheric waves called lunar tides using electron density data from the COSMIC-2 satellite (GIS), vertical plasma drifts from NASA’s ICON mission, and simulations from the SD-WACCM-X and TIE-GCM model.

B. Maletckii, E. Astafyeva, N. M. Pedatella, and L. Qian use high-rate 1Hz data of ionospheric total electron content (TEC) and we analyze ionospheric effects of 13 solar flares that occurred between 2003 and 2023. For the first time, we demonstrate that the SID first appears at the subsolar point (i.e., the point where the Sun is directly overhead), and further expands to the twilight regions at a very high speed.

Schad, Bryans, Fehlmann, Gibson, Harrington, Tarr, Tomczyk, and Yepez compare externally occulted coronagraphic measurements of near-Sun radiance with aerosol-constrained inferences derived from direct-Sun and sky photometry—focusing on the Mauna Loa Observatory, a well-characterized high-altitude site for atmospheric and solar observations.