@article{Desai:2022:1538-4357/ac4961,
author = {Desai, M and Mitchell, DG and McComas, DJ and Drake, JF and Phan, T and Szalay, JR and Roelof, EC and Giacalone, J and Hill, ME and Christian, ER and Schwadron, NA and McNutt, RL and Wiedenbeck, ME and Joyce, C and Cohen, CMS and Davis, AJ and Krimigis, SM and Leske, RA and Matthaeus, WH and Malandraki, O and Mewaldt, RA and Labrador, A and Stone, EC and Bale, SD and Verniero, J and Rahmati, A and Whittlesey, P and Livi, R and Larson, D and Pulupa, M and MacDowall, RJ and Niehof, JT and Kasper, JC and Horbury, TS},
doi = {1538-4357/ac4961},
journal = {The Astrophysical Journal: an international review of astronomy and astronomical physics},
pages = {1--12},
title = {Suprathermal ion energy spectra and anisotropies near the heliospheric current sheet crossing observed by the Parker Solar Probe during encounter 7},
url = {http://dx.doi.org/10.3847/1538-4357/ac4961},
volume = {927},
year = {2022}
}

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TY  - JOUR
AB  - We present observations of 10–100 keV nucleon−1 suprathermal (ST) H, He, O, and Fe ions associated with crossings of the heliospheric current sheet (HCS) at radial distances of <0.1 au from the Sun. Our key findings are as follows: (1) very few heavy ions are detected during the first full crossing, the heavy-ion intensities are reduced during the second partial crossing and peak just after the second crossing; (2) ion arrival times exhibit no velocity dispersion; (3) He pitch-angle distributions track the magnetic field polarity reversal and show up to ∼10:1 anti-sunward, field-aligned flows and beams closer to the HCS that become nearly isotropic farther from the HCS; (4) the He spectrum steepens either side of the HCS, and the He, O, and Fe spectra exhibit power laws of the form ∼E−4–E6; and (5) maximum energies EX increase with the ion's charge-to-mass (Q/M) ratio as ${E}_{X}/{E}_{H}\propto {({Q}_{X}/{M}_{X})}^{\delta }$, where δ ∼ 0.65–0.76, assuming that the average Q states are similar to those measured in gradual and impulsive solar energetic particle events at 1 au. The absence of velocity dispersion in combination with strong field-aligned anisotropies closer to the HCS appears to rule out solar flares and near-Sun coronal-mass-ejection-driven shocks. These new observations present challenges not only for mechanisms that employ direct parallel electric fields and organize maximum energies according to E/Q but also for local diffusive and magnetic-reconnection-driven acceleration models. Reevaluation of our current understanding of the production and transport of energetic ions is necessary to understand this near-solar, current-sheet-associated population of ST ions.
AU  - Desai,M
AU  - Mitchell,DG
AU  - McComas,DJ
AU  - Drake,JF
AU  - Phan,T
AU  - Szalay,JR
AU  - Roelof,EC
AU  - Giacalone,J
AU  - Hill,ME
AU  - Christian,ER
AU  - Schwadron,NA
AU  - McNutt,RL
AU  - Wiedenbeck,ME
AU  - Joyce,C
AU  - Cohen,CMS
AU  - Davis,AJ
AU  - Krimigis,SM
AU  - Leske,RA
AU  - Matthaeus,WH
AU  - Malandraki,O
AU  - Mewaldt,RA
AU  - Labrador,A
AU  - Stone,EC
AU  - Bale,SD
AU  - Verniero,J
AU  - Rahmati,A
AU  - Whittlesey,P
AU  - Livi,R
AU  - Larson,D
AU  - Pulupa,M
AU  - MacDowall,RJ
AU  - Niehof,JT
AU  - Kasper,JC
AU  - Horbury,TS
DO  - 1538-4357/ac4961
EP  - 12
PY  - 2022///
SN  - 0004-637X
SP  - 1
TI  - Suprathermal ion energy spectra and anisotropies near the heliospheric current sheet crossing observed by the Parker Solar Probe during encounter 7
T2  - The Astrophysical Journal: an international review of astronomy and astronomical physics
UR  - http://dx.doi.org/10.3847/1538-4357/ac4961
UR  - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000764328700001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/ac4961
UR  - http://hdl.handle.net/10044/1/99032
VL  - 927
ER  - 

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