ORIGINAL RESEARCH article
Front. Astron. Space Sci.
Sec. Space Physics
Composition dependence of ion heating in dayside magnetopause reconnection: MMS observations
Provisionally accepted
Elizabeth Hanson1*
Laura Balboa1Alayna Corona1Cynthia A. Cattell1Evan Tyler2Tai D. Phan3
Stephen A Fuselier4,5Roman G. Gomez4- 1University of Minnesota Twin Cities, St. Paul, United States
- 2The College of St Scholastica, Duluth, United States
- 3University of California Berkeley, Berkeley, United States
- 4Southwest Research Institute, San Antonio, United States
- 5The University of Texas at San Antonio, San Antonio, United States
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Motivated by observed composition dependence in reconnection energy outflow and by theoretical and simulation studies predicting differences between heating of H+ and heavier ions, we investigated the ion composition dependence of heating associated with reconnection in 28 dayside magnetopause crossings in Magnetospheric Multiscale (MMS) data. Available magnetic energy per ion-electron pair flowing into the magnetopause from the magnetosheath and magnetosphere ranged between a few tens of eV and ~1750 eV. We applied Least Squares fitting to analyze the relationship of temperature change across the magnetopause exhaust to available magnetic energy. The individual fits for composition-nonspecific ions and for H+ were significantly lower than the empirical scaling relationship between the asymmetric Alfvén speed and inflowing magnetic energy found previously; the fit for He++ was higher, with marginal significance. A composite data product combining H+ and He++ agreed with the empirical scaling relationship to within 95%. Although comparisons between heating of H+ and He++ are suggestive of enhanced heating of heavy ions, differences could not be identified conclusively due to high scatter and a small number of events with adequate densities of heavy ions.
Keywords: dayside magnetopause, Heavy Ions, Ion composition, Ion heating, magnetic reconnection
Received: 18 Nov 2025; Accepted: 29 Dec 2025.
Copyright: © 2025 Hanson, Balboa, Corona, Cattell, Tyler, Phan, Fuselier and Gomez. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Elizabeth Hanson
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