Phil Judge

Changing methodologies in solar physics

whawkins — Wed, 16 Apr 2025 16:07:01 +0000

Changing methodologies in solar physics whawkins Wed, 04/16/2025 - 10:07

Author:

whawkins

Apr 16, 2025

Solar Physics (submitted): This study attempts to establish a basis for understanding how methods used in research in solar physics have evolved since WWII. The goal is to begin to explore if and how the changing research environment affects the training of young scientists, and the future of solar physics research at our institutions. A strategy based upon a sample of 650 PhD theses is used to assess research. The statistical analysis is based upon necessarily subjective categorization and the inference of likelihoods of two different distributions being drawn from the same underlying distribution. The data suggest that impactful advances are becoming more rare, but the methods used have changed little barring those related to obvious technological advances (e.g. the advent of spacecraft, adaptive optics). A follow-up study to explore the 100,000+ publications in solar physics through machine learning seems warranted.

The sample of 650 PhD theses used in the study is shown at the top, with relevant events shown in lower panels

On the intermittency of hot plasma loops in the solar corona

whawkins — Tue, 20 Aug 2024 16:58:20 +0000

On the intermittency of hot plasma loops in the solar corona whawkins Tue, 08/20/2024 - 10:58

Author:

whawkins

Aug 20, 2024

APJ: Why and how are entire hydromagnetic structures only intermittently loaded with bright coronal plasma in the Sun? The present work scrutinizes more chromospheric and coronal data, with the aim of finding reproducible observational constraints on coronal heating mechanisms. Six independent scans of chromospheric active region magnetic fields are investigated and correlated to overlying hot plasma loops. For the first time, the footpoints of over 30 bright plasma loops are thus related to scalar proxies for the Poynting fluxes measured from the upper chromosphere. Although imperfect, the proxies all indicate a general lack of correlation between footpoint Poynting flux and loop brightness. Our findings consolidate the claim that unobserved physical processes are at work which govern the heating of long-lived coronal loops.

Footpoints of the solar coronal emission (red) do not correlate either with line of sight magnetic fields in the chromosphere (top) or with the estimate of electromagnetic energy emerging from the chromosphere (bottom panel). Data from SDO and DKIST are shown.

Erratum: Analysis of Seeing-Induced Polarization Cross-Talk and Modulation Scheme Performance

whawkins — Thu, 01 Aug 2024 15:39:00 +0000

Erratum: Analysis of Seeing-Induced Polarization Cross-Talk and Modulation Scheme Performance whawkins Thu, 08/01/2024 - 09:39

Author:

whawkins

Aug 1, 2024

Corrected Figure 7 of Paper I, showing the polarimetric errors for a stepped waveplate with 150◦ retardance (8-state modulation scheme), with dual-beam analysis, and 10 s integration. For this example, we adopted a non-optimal demodulation scheme consisting of simple additions and subtractions of individual modulated signals.

The Astrophysical Journal: (Published 2012 September 4; submitting a "corrected" Figure 7 of Paper I) We analyze the generation of polarization cross-talk in Stokes polarimeters by atmospheric seeing, and its effects on the noise statistics of spectropolarimetric measurements for both single-beam and dual-beam instruments. We investigate the time evolution of seeing-induced correlations between different states of one modulation cycle and compare the response to these correlations of two popular polarization modulation schemes in a dual-beam system. Extension of the formalism to encompass an arbitrary number of modulation cycles enables us to compare our results with earlier work. Even though we discuss examples pertinent to solar physics, the general treatment of the subject and its fundamental results might be useful to a wider community.

Magnetic fields beneath active region coronal loops

whawkins — Thu, 09 May 2024 14:09:07 +0000

Magnetic fields beneath active region coronal loops whawkins Thu, 05/09/2024 - 08:09

Author:

whawkins

May 9, 2024

The Astrophysical Journal: Using measurements of photospheric and chromospheric magnetic fields from the GREGOR GRIS instrument, the paper refutes the idea that magnetic reconnection of network magnetic fields with granular fields drives coronal heating. Instead heating arises within primarily unipolar fields above the chromosphere.

Upper panels show measurements of photospheric chromospheric magnetic fields which are unipolar (black contours containing strong magnetic flux), and only very weak fields of opposite polarity far from the unipolar fields (red and blue). The lower panels show emission from overlying transition region and coronal plasma, associated almost completely with unipolar fields far from minority polarity concentrations.

New Book! The Problem of Coronal Heating: A Rosetta Stone for Electrodynamic Coupling in Cosmic Plasmas

kolinski — Mon, 25 Mar 2024 15:28:28 +0000

New Book! The Problem of Coronal Heating: A Rosetta Stone for Electrodynamic Coupling in Cosmic Plasmas kolinski Mon, 03/25/2024 - 09:28

By Philip Judge and James A. Ionson

Author:

kolinski

Mar 25, 2024

HAO is pleased to announce the publication of a new and timely book written for young and open-minded scientists just prior to the total eclipse over the USA in April. Senior scientist Philip Judge and co-author James A. Ionson ask why, 8 decades after Bengt Edlen published his seminal article, we still do not have a clear answer to one of the longest-lasting puzzles in all of astronomy. Why is the solar corona so hot?

Cover of Phil Judge's book, The Problem of Coronal Heating

The book offers deep insights during the modern era of major advances in experimentation, with new telescopes on the ground and multiple novel spacecraft -- some orbiting within the corona itself. It serves as a needed new resource for all of astronomy concerned with the coupling of gravitationally-bound objects such as stars, black holes, and galaxies to their environment, through electromagnetic forces.

The publisher's web page contains further information about the text and the authors: https://link.springer.com/book/10.1007/978-3-031-46273-3

Anyone interested can also watch Phil's colloqiuium video that presents just a few nuggets, including such things as radio jets, chocolate cake, and the Rolling Stones.

New Book: The Problem of Coronal Heating

whawkins — Fri, 15 Sep 2023 17:47:04 +0000

New Book: The Problem of Coronal Heating whawkins Fri, 09/15/2023 - 11:47

Author:

whawkins

Sep 15, 2023

A Rosetta Stone for Electrodynamic Coupling in Cosmic Plasmas—This new book reflects on 8 decades of research on one of the longest-standing unsolved problems in modern physics: why exactly is the Sun obliged to form a hot corona? The Sun's corona is our closest example of the inevitable "'electrodynamic coupling" between a condensed astronomical object and its environment. It is a local "Rosetta Stone" \index{Rosetta~Stone} for understanding hot plasmas across the Universe. The authors offer a critical overview of the field of research, including a dive into methodologies to understand the nature of this recalcitrant problem. Armed with an up-to-date understanding of theory, instrumentation, and the developing field of machine learning, the authors offer suggestions for new, stronger methodologies aimed to generate measurable progress. Written for aspiring astrophysicists, students of physics and active researchers, the book highlights the irony of why astrophysical plasmas, so nearly ideal, must lead to their own imperfect dissipation of magnetic energy, forming the hot coronae of stars and many more exotic objects. With a fresh perspective, the book offers a straightforward, physical guide to the next generation of researchers who wish to cut to the chase, to finally lay the problem to rest, with implications for a technological society that is subject to the electrodynamic whims and vagaries of its host star.

Book cover: The Problem of Coronal Heating—A Rosetta Stone for Electrodynamic Coupling in Cosmic Plasmas

Magnetic fields and plasma heating in the Sun’s atmosphere

whawkins — Fri, 15 Sep 2023 17:46:44 +0000

Magnetic fields and plasma heating in the Sun’s atmosphere whawkins Fri, 09/15/2023 - 11:46

Author:

whawkins

Sep 15, 2023

Close-up views of the magnetic structure as measured by DKIST (upper four panels) are compared with the upper atmosphere (lower four panels) as measured using instruments on the IRIS and SDO spacecraft. The shocking lack of identifiable magnetic structure in the chromosphere (row 2, first panel) just beneath the highly structured corona (bottom right panel) reveals that coronal heating problem contains variables hidden from our ability to deserve. The 8 decade-old problem must be re-formulated to address the conclusion that “the corona is a self-regulating forced system” (Einaudi et al. 2021). A paradigm change seems in order.

ApJ: The paper uniquely connects magnetic fields threading the chromosphere to the overlying corona and other heated plasmas. No correlations were found between heated plasma and properties of chromospheric magnetic fields on scales below supergranules. Processes hidden from our observations control plasma heating. While improved magnetic measurements are needed, these data indicate that the corona is a self-regulating forced system. Heating depends on the state of the corona, not simply on boundary conditions. Heating models based upon identifiable bipolar fields, including cool loops, tectonics and observable magnetic reconnection, are refuted for these regions with unipolar chromospheric magnetic fields.

Steadiness of coronal heating

whawkins — Wed, 16 Aug 2023 16:59:38 +0000

Steadiness of coronal heating whawkins Wed, 08/16/2023 - 10:59

Author:

whawkins

Aug 16, 2023

The Astrophysical Journal: The EUI instrument on the Solar Orbiter spacecraft has obtained the most stable, high-resolution images of the solar corona from its orbit with a perihelion near 0.4 AU. A sequence of 360 images obtained at 17.1 nm, between 25-Oct-2022 19:00 and 19:30 UT is scrutinized. One image pixel corresponds to 148 km at the solar surface. The widely-held belief that the outer atmosphere of the Sun is in a continuous state of magnetic turmoil is pitted against the EUI data. The observed plasma variations appear to fall into two classes. By far the dominant behavior is a very low amplitude variation in brightness (1%) in the coronal loops, with larger variations in some footpoint regions. No hints of observable changes in magnetic topology are associated with such small variations. The larger amplitude, more rapid, rarer and less-well organized changes are associated with flux emergence. It is suggested therefore that while magnetic reconnection drives the latter, most of the active corona is heated with no evidence of a role for large-scale (observable) reconnection. Since most coronal emission line widths are subsonic, the bulk of coronal heating, if driven by reconnection, can only be of tangentially discontinuous magnetic fields, with angles below about 0.5cS/cA ∼ 0.3β, with β the plasma beta parameter (∼ 0.01), and cS and cA sound and Alfv´en speeds. If heated by multiple small flare-like events, then these must be 1020 erg or less, i.e. pico-flares. But processes other than reconnection have yet to be ruled out, such as viscous dissipation, which may contribute to the steady heating of coronal loops over active regions.

A figure showing data from Solar Orbiter EUI at 17.1 nm, revealing two kinds of behavior: steady heating associated with coronal loops and unsteady heating associated only with emerging magnetic flux.

First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP

whawkins — Tue, 04 Apr 2023 16:33:16 +0000

First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP whawkins Tue, 04/04/2023 - 10:33

The Anatomy of an Umbral Flash

Author:

whawkins

Apr 4, 2023

Astrophysical Journal Letters: The Visible Spectro-Polarimeter of the NSF Daniel K. Inouye Solar Telescope collected its Science Verification data on 2021 May 7-8. The instrument observed multiple layers of a sunspot atmosphere simultaneously, in passbands of Ca II 397 nm (H line), Fe I 630 nm, and Ca II 854 nm, scanning the region with a spatial sampling of 0.04 arcsec1 and an average temporal cadence of 7.76 s, for a duration of 38.8 minutes. The slit moved southward across the plane of sky at 3.83 km s-1. The spectropolarimetric scans exhibit prominent oscillatory "ridge" structures that lie nearly perpendicular to the direction of slit motion (north to south). These ridges are visible in the maps of line intensity, central wavelength, line width, and both linear and circular polarization. Contemporaneous Atmospheric Imaging Assembly observations indicate that these ridges are purely temporal in character and are likely attributed to the familiar chromospheric 3 minute umbral oscillations. We observe in detail a steady umbral flash near the center of the sunspot umbra. Although bad seeing limited the spatial resolution, the unique high signal-to-noise ratio data enable us to estimate the shock Mach numbers (~2), propagation speeds (~9 km/s), and their impacts on the longitudinal magnetic field (dB ~ 50 G), gas pressure, and temperature (dT/T ~ 0.1) of subshocks over 30 s. We also find evidence for rarefaction waves situated between neighboring wave train shocks. The Ca II 854 nm line width is fairly steady throughout the umbral flash, except for a sharp 1.5 km/s dip immediately before, and a comparable spike immediately after, the passage of the shock front. This zigzag in line width is centered on the subshock and extends over 0.4 arcsec.

Detrended intensity, line width, azimuth, P, and B LOS cross sections, and raw Doppler cross sections, along the dashed cyan and magenta lines. The vertical dashed lines show the approximate locations of the Ca II 854 nm intensity peaks.

First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP

whawkins — Wed, 15 Mar 2023 16:08:51 +0000

First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP whawkins Wed, 03/15/2023 - 10:08

Phil Judge

Changing methodologies in solar physics

Recent News

On the intermittency of hot plasma loops in the solar corona

Recent News

Erratum: Analysis of Seeing-Induced Polarization Cross-Talk and Modulation Scheme Performance

Recent News

Magnetic fields beneath active region coronal loops

Recent News

New Book! The Problem of Coronal Heating: A Rosetta Stone for Electrodynamic Coupling in Cosmic Plasmas

Recent News

New Book: The Problem of Coronal Heating

Recent News

Magnetic fields and plasma heating in the Sun’s atmosphere

Recent News

Steadiness of coronal heating

Recent News

First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP

Recent News

First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP

Recent News