TY - JOUR
T1 - In Situ Measurement of the Energy Fraction in Suprathermal and Energetic Particles at ACE, Wind, and PSP Interplanetary Shocks
AU - David, Liam
AU - Fraschetti, Federico
AU - Giacalone, Joe
AU - Wimmer-Schweingruber, Robert F.
AU - Berger, Lars
AU - Lario, David
N1 - Funding Information:
This paper uses data from the Center for Astrophysics ∣ Harvard & Smithsonian Interplanetary Shock Database ( https://lweb.cfa.harvard.edu/shocks/ ). We thank Dr. M. Stevens for providing us with guidance on the database, Dr. M. Pulupa for suggestions on the PSP event, and Dr. L. Wilson III for help with Wind/PESA data. The material contained in this document is based upon work supported by a National Aeronautics and Space Administration (NASA) grant or cooperative agreement. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NASA. This work was supported through a NASA grant awarded to the Arizona/NASA Space Grant Consortium. This work was also supported in part by NASA grant No. 80NSSC20K1283 as part of the Heliophysics System Observatory Connect Program. F.F. was supported, in part, by NSF under grant No. 1850774, and by NASA under grant Nos. 80NSSC18K1213, 80NSSC20K1283, 80NSSC21K0119, and the Chandra Theory Award Number TM0-21001X, issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. J.G. was supported, in part, by NASA under grants 80NSSC18K1213, 80NSSC20K1283, and 80NSSC21K0119. D.L. acknowledges support from NASA HGI grant No. NNX16AF73G and the Living With a Star (LWS) programs NNH17ZDA001N-LWS and NNH19ZDA001N-LWS, as well as the Goddard Space Flight Center Heliophysics Innovation Fund (HIF) program.
Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
PY - 2022/3/1
Y1 - 2022/3/1
N2 - The acceleration of charged particles by interplanetary shocks (IPs) can drain a nonnegligible fraction of the plasma pressure. In this study, we have selected 17 IPs observed in situ at 1 au by the Advanced Composition Explorer and the Wind spacecraft, and 1 shock at 0.8 au observed by Parker Solar Probe. We have calculated the time-dependent partial pressure of suprathermal and energetic particles (smaller and greater than 50 keV for protons and 30 keV for electrons, respectively) in both the upstream and downstream regions. The particle fluxes were averaged for 1 hr before and 1 hr after the shock time to remove short timescale effects. Using the MHD Rankine-Hugoniot jump conditions, we find that the fraction of the total upstream energy flux transferred to suprathermal and energetic downstream particles is typically ≤ 16%, in agreement with previous observations and simulations. Notably, by accounting for errors on all measured shock parameters, we have found that for any given fast magnetosonic Mach number, M f < 7, the angle between the shock normal and average upstream magnetic field, θ Bn, is not correlated with the energetic particle pressure; in particular, the partial pressure of energized particles does not decrease for θ Bn ≥ 45°. The downstream electron-to-proton energy ratio in the range ≥ 140 eV for electrons and ≥ 70 keV for protons exceeds the expected ∼1% and nears equipartition (>0.1) for the Wind events.
AB - The acceleration of charged particles by interplanetary shocks (IPs) can drain a nonnegligible fraction of the plasma pressure. In this study, we have selected 17 IPs observed in situ at 1 au by the Advanced Composition Explorer and the Wind spacecraft, and 1 shock at 0.8 au observed by Parker Solar Probe. We have calculated the time-dependent partial pressure of suprathermal and energetic particles (smaller and greater than 50 keV for protons and 30 keV for electrons, respectively) in both the upstream and downstream regions. The particle fluxes were averaged for 1 hr before and 1 hr after the shock time to remove short timescale effects. Using the MHD Rankine-Hugoniot jump conditions, we find that the fraction of the total upstream energy flux transferred to suprathermal and energetic downstream particles is typically ≤ 16%, in agreement with previous observations and simulations. Notably, by accounting for errors on all measured shock parameters, we have found that for any given fast magnetosonic Mach number, M f < 7, the angle between the shock normal and average upstream magnetic field, θ Bn, is not correlated with the energetic particle pressure; in particular, the partial pressure of energized particles does not decrease for θ Bn ≥ 45°. The downstream electron-to-proton energy ratio in the range ≥ 140 eV for electrons and ≥ 70 keV for protons exceeds the expected ∼1% and nears equipartition (>0.1) for the Wind events.
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U2 - 10.3847/1538-4357/ac54af
DO - 10.3847/1538-4357/ac54af
M3 - Article
AN - SCOPUS:85128115524
VL - 928
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
M1 - 66
ER -