Sciences and Exploration Directorate

Joel C Allred


Joel C Allred's Contact Card & Information.
Phone: 301.286.6892
Org Code: 671
Mail Code 671
Greenbelt, MD 20771

Brief Bio

I am a research solar physicist in the Heliophysics Division of NASA's Goddard Space Flight Center.

Research Interests

Solar flares

Heliophysics: Transient Events

I am active in researching the hydrodynamic evolution of solar flares. Specifically, in modeling the radiation produced in response to solar flare heating. I also study the transport of flare-accelerated particles through the solar atmosphere and how these heat and deposit momentum throughout the solar atmosphere.

Modeling radiative transfer

Heliophysics: Theory & Modeling

I model the transfer of radiation produced during solar flares. Specifically, I focus on the non-LTE, optically-thick, radiation produced in the solar chromosphere, but I also model emission lines in the optically thin corona. A particularly long-standing interest of mine is to understand the origin of white light flares.

Modeling particle transport at the kinetic scale

Heliophysics: Theory & Modeling

I am interested in modeling the transport of non-thermal particles accelerated during solar flares. To do this, I have developed a numerical code to solve the Fokker-Planck equation for conditions appropriate to the solar corona and into the chromosphere.


Research Astrophysicist

NASA - Goddard Space Flight Center

September 2010 - Present

IRIS Deputy Project Scientist

NASA - Goddard Space Flight Center

2013 - Present


2005 Ph.D., Department of Physics, University of Washington, Seattle, WA

Professional Societies

American Astronomical Society - Solar Physics Division

2003 - Present

American Geophysical Union

2005 - Present

Professional Service

I serve on Goddard's LGBTQ+ Employee Resource Group


2019 Robert H. Goddard Award for Science

2020 Agency Early Career Achievement Medal

Selected Publications


2022. "Solar Flare Heating with Turbulent Suppression of Thermal Conduction." The Astrophysical Journal 931 (1): 60 [10.3847/1538-4357/ac69e8] [Journal Article/Letter]

2022. "The Atmospheric Response to High Nonthermal Electron-beam Fluxes in Solar Flares. II. Hydrogen-broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope." The Astrophysical Journal 928 (2): 190 [10.3847/1538-4357/ac5174] [Journal Article/Letter]

2022. "Probing the Physics of the Solar Atmosphere with the Multi-slit Solar Explorer (MUSE). II. Flares and Eruptions." The Astrophysical Journal 926 (1): 53 [10.3847/1538-4357/ac4223] [Journal Article/Letter]

2021. "Role of Suprathermal Runaway Electrons Returning to the Acceleration Region in Solar Flares." The Astrophysical Journal 917 (2): 74 [10.3847/1538-4357/ac0820] [Journal Article/Letter]

2021. "He i 10830 Å Dimming during Solar Flares. I. The Crucial Role of Nonthermal Collisional Ionizations." The Astrophysical Journal 912 (2): 153 [10.3847/1538-4357/abf42d] [Journal Article/Letter]

2020. "Modeling the Transport of Nonthermal Particles in Flares Using Fokker-Planck Kinetic Theory." The Astrophysical Journal 902 (1): 16 [10.3847/1538-4357/abb239] [Journal Article/Letter]

2020. "Solar Flare Arcade Modeling: Bridging the Gap from 1D to 3D Simulations of Optically Thin Radiation." The Astrophysical Journal 900 (1): 18 [10.3847/1538-4357/abaa46] [Journal Article/Letter]

2020. "Optical and X-ray observations of stellar flares on an active M dwarf AD Leonis with the Seimei Telescope, SCAT, NICER, and OISTER." Publications of the Astronomical Society of Japan 72 (4): [10.1093/pasj/psaa051] [Journal Article/Letter]

2020. "Spectral Characteristics and Formation Height of Off-limb Flare Ribbons." The Astrophysical Journal 896 (2): 120 [10.3847/1538-4357/ab9603] [Journal Article/Letter]

2020. "Spectral Signatures of Chromospheric Condensation in a Major Solar Flare." The Astrophysical Journal 895 (1): 6 [10.3847/1538-4357/ab88ad] [Journal Article/Letter]

2019. "Modeling Mg ii during Solar Flares. II. Nonequilibrium Effects." The Astrophysical Journal 885 (2): 119 [10.3847/1538-4357/ab48ea] [Journal Article/Letter]

2019. "Modeling Mg II During Solar Flares. I. Partial Frequency Redistribution, Opacity, and Coronal Irradiation." The Astrophysical Journal 883 (1): 57 [10.3847/1538-4357/ab3c24] [Journal Article/Letter]

2019. "Modeling Mg ii h, k and Triplet Lines at Solar Flare Ribbons." The Astrophysical Journal 879 (1): 19 [10.3847/1538-4357/ab2238] [Journal Article/Letter]

2019. "Spectral Evidence for Heating at Large Column Mass in Umbral Solar Flare Kernels. I. IRIS Near-UV Spectra of the X1 Solar Flare of 2014 October 25." The Astrophysical Journal 878 (2): 135 [10.3847/1538-4357/ab1f8b] [Journal Article/Letter]

2019. "SI iv Resonance Line Emission during Solar Flares: Non-LTE, Nonequilibrium, Radiation Transfer Simulations." The Astrophysical Journal 871 (1): 23 [10.3847/1538-4357/aaf46e] [Journal Article/Letter]

2018. "Reproducing Type II White-light Solar Flare Observations with Electron and Proton Beam Simulations." The Astrophysical Journal 862 (1): 76 [10.3847/1538-4357/aaca37] [Journal Article/Letter]

2017. "Hydrogen Balmer Line Broadening in Solar and Stellar Flares." The Astrophysical Journal 837 (2): 125 [10.3847/1538-4357/aa603e] [Journal Article/Letter]

2017. "The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. I. Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29." The Astrophysical Journal 836 (1): 12 [10.3847/1538-4357/836/1/12] [Journal Article/Letter]

2017. "Solar Ellerman Bombs in 1D Radiative Hydrodynamics." The Astrophysical Journal 835 (2): L37 [10.3847/2041-8213/835/2/l37] [Journal Article/Letter]

2016. "OBSERVATIONS AND SIMULATIONS OF THE Na i D1LINE PROFILES IN AN M-CLASS SOLAR FLARE." The Astrophysical Journal 832 (2): 147 [10.3847/0004-637x/832/2/147] [Journal Article/Letter]

2016. "DATA-DRIVEN RADIATIVE HYDRODYNAMIC MODELING OF THE 2014 MARCH 29 X1.0 SOLAR FLARE." The Astrophysical Journal 827 (1): 38 [10.3847/0004-637x/827/1/38] [Journal Article/Letter]

2016. "Simulations of the Mg II k and Ca II 8542 lines from an Alfven Wave-heated Flare Chromosphere." The Astrophysical Journal 827 (2): 101 [Journal Article/Letter]

2015. "HαLINE PROFILE ASYMMETRIES AND THE CHROMOSPHERIC FLARE VELOCITY FIELD." The Astrophysical Journal 813 (2): 125 [10.1088/0004-637x/813/2/125] [Journal Article/Letter]

2015. "A Unified Computational Model for Solar and Stellar Flares." Astrophysical Journal 809 (104): 14pp [10.1088/0004-637X/809/1/104] [Journal Article/Letter]

2015. "New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation." Solar Physics 290 (12): 3487-3523 [10.1007/s11207-015-0708-x] [Journal Article/Letter]

2015. "Radiative hydrodynamic modelling and observations of the X-class solar flare on 2011 March 9." Astronomy & Astrophysics 578 A72 [10.1051/0004-6361/201425144] [Journal Article/Letter]

2014. "Evidence of nonthermal particles in coronal loops heated impulsively by nanoflares." Science 346 (6207): [10.1126/science.1255724] [Journal Article/Letter]


2011. "IONIC COMPOSITION STRUCTURE OF CORONAL MASS EJECTIONS IN AXISYMMETRIC MAGNETOHYDRODYNAMIC MODELS." The Astrophysical Journal 740 (2): 112 [10.1088/0004-637x/740/2/112] [Journal Article/Letter]

2007. "Near‐Ultraviolet Spectra of Flares on YZ CMi." Publications of the Astronomical Society of the Pacific 119 (851): 67-81 [10.1086/510561] [Journal Article/Letter]

2006. "Radiative Hydrodynamic Models of Optical and Ultraviolet Emission from M Dwarf Flares." The Astrophysical Journal 644 (1): 484-496 [10.1086/503314] [Journal Article/Letter]

2006. "Optical Spectroscopy of a Flare on Barnard's Star." Publications of the Astronomical Society of the Pacific 118 227-235 [10.1086/499497] [Journal Article/Letter]

2006. "From Radio to X-Ray: The Quiescent Atmosphere of the dMe Flare Star EV Lacertae." The Astrophysical Journal 647 1349-1374 [10.1086/504889] [Journal Article/Letter]

2005. "Radiative Hydrodynamic Models of the Optical and Ultraviolet Emission from Solar Flares." The Astrophysical Journal 630 (1): 573-586 [10.1086/431751] [Journal Article/Letter]

2005. "From Radio to X‐Ray: Flares on the dMe Flare Star EV Lacertae." The Astrophysical Journal 621 (1): 398-416 [10.1086/427275] [Journal Article/Letter]

2005. "TRACE white light and RHESSI hard X-rays." AGU Fall Meeting Abstracts A286- [Journal Article/Letter]

2004. "Multi-Wavelength Observations of EV Lacertae." Stars as Suns : Activity - Evolution and Planets 219 249- [Journal Article/Letter]

2003. "Multiwavelength Observations of Flares on AD Leonis." The Astrophysical Journal 597 (1): 535-554 [10.1086/378351] [Journal Article/Letter]