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Abstract We present in this Letter the first global comparison between traditional line-tied steady-state magnetohydrodynamic models and a new, fully time-dependent thermodynamic magnetohydrodynamic simulation of the global corona. To approximate surface magnetic field distributions and magnitudes around solar minimum, we use the Lockheed Evolving Surface-Flux Assimilation Model to obtain input maps that incorporate flux emergence and surface flows over a full solar rotation, including differential rotation and meridional flows. Each time step evolves the previous state of the plasma with a new magnetic field input boundary condition, mimicking photospheric driving on the Sun. We find that this method produces a qualitatively different corona compared to steady-state models. The magnetic energy levels are higher in the time-dependent model, and coronal holes evolve more along the following edge than they do in steady-state models. Coronal changes, as illustrated with forward-modeled emission maps, evolve on longer timescales with time-dependent driving. We discuss implications for active and quiet Sun scenarios, solar wind formation, and widely used steady-state assumptions like potential field source surface calculations.
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Hidden Activity Revealed: Photospheric Energetics and Dynamics with High-resolution Magnetographic Data
Abstract We revisit an existing but unexplored finding on the calculation of the baseline (i.e., potential) magnetic energy in observed solar magnetic configurations and apply it to two series of high-cadence, cospatial, and cotemporal line-of-sight photospheric magnetograms with a factor of ∼4 difference in spatial resolution. The target is a small coronal hole, ∼80″across. We find significant differences between the two data sets, with approximate factors of 2.4 in the unsigned magnetic flux, 2.1 in the potential magnetic energy, and 5.2 in the mean amplitudes of the energy variation, all in favor of the higher-resolution magnetograms. Additionally, we find a factor of 2.5 difference in the characteristic magnetic flux replenishment time, with configurations at higher resolution renewing their flux every 46 minutes on average. Energy decreases associated with apparent magnetic flux cancellation events in higher resolution yield power densities above 106erg cm−2s−1, seemingly sufficient to sustain coronal holes and drive the fast solar wind. For the first time, this represents apparent energy released at photospheric altitudes rather than energy deposited via the Poynting flux. Lower-resolution magnetograms give 5.4 times less power density output. These intriguing results could have wide-ranging implications for in situ solar wind measurements and their solar sources in the Parker Solar Probe mission, as well as for high-resolution observations featuring simultaneous photospheric and chromospheric magnetograms including, but not limited to, data from the Daniel K. Inouye Solar Telescope.
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- PAR ID:
- 10648203
- Publisher / Repository:
- American Astronomical Society
- Date Published:
- Journal Name:
- The Astrophysical Journal Letters
- Volume:
- 990
- Issue:
- 1
- ISSN:
- 2041-8205
- Page Range / eLocation ID:
- L6
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3847/2041-8213/adf849
