TY - JOUR

T1 - The Statistical Properties of Solar Wind Temperature Parameters Near 1 au

AU - Wilson, Lynn B.

AU - Stevens, Michael L.

AU - Kasper, Justin C.

AU - Klein, Kristopher G.

AU - Maruca, Bennett A.

AU - Bale, Stuart D.

AU - Bowen, Trevor A.

AU - Pulupa, Marc P.

AU - Salem, Chadi S.

N1 - Funding Information:
The authors thank A.F.-Viñas and T. Nieves-Chinchilla for useful discussions of solar wind plasma physics. L.B.W. was partially supported by Wind MO&DA grants. C.S.S. was partially supported by NASA grant NNX16AI59G and NSF SHINE grant 1622498. S.D.B., T.A.B., C.S.S., and M.P.P. were partially supported by NASA grant NNX16AP95G. M.P.P. was also partially supported by NASA grant NNX14AC09G. B.A.M. was partially supported by NASA grants NNX17AC 72G and NNX17AH88G. K.G.K. and J.C.K. were partially supported by NASA grant NNX14AR78G. M.L.S. was partially supported by grants NNX14AT26G and NNX13AI75G. The CFA Interplanetary Shock Database is supported by NASA grant NNX13AI75G. The authors thank the Harvard Smithsonian Center for Astrophysics, the NASA SPDF/CDAWeb team, and the Wind team for the interplanetary shock analysis, Wind plasma and magnetic field data, and the Wind ICME catalog, respectively. The Wind shock database can be found athttps://www.cfa. harvard.edu/shocks/wi_data/. The Wind ICME catalog can be found athttps://wind.nasa.gov/ICMEindex.php. The analysis software used herein can be found at https://github.com/ lynnbwilsoniii/wind_3dp_pros.

PY - 2018/6

Y1 - 2018/6

N2 - We present a long-duration (∼10 yr) statistical analysis of the temperatures, plasma betas, and temperature ratios for the electron, proton, and alpha-particle populations observed by the Wind spacecraft near 1 au. The mean(median) scalar temperatures are T e,tot = 12.2(11.9) eV, T p,tot = 12.7(8.6) eV, and T α,tot = 23.9(10.8) eV. The mean(median) total plasma betas are β e,tot = 2.31(1.09), β p,tot = 1.79(1.05), and β α,tot = 0.17(0.05). The mean(median) temperature ratios are (T e/T p)tot = 1.64(1.27), (T e/T α)tot = 1.24(0.82), and (T α/T p)tot = 2.50(1.94). We also examined these parameters during time intervals that exclude interplanetary (IP) shocks, times within the magnetic obstacles (MOs) of interplanetary coronal mass ejections (ICMEs), and times that exclude MOs. The only times that show significant alterations to any of the parameters examined are those during MOs. In fact, the only parameter that does not show a significant change during MOs is the electron temperature. Although each parameter shows a broad range of values, the vast majority are near the median. We also compute particle-particle collision rates and compare to effective wave-particle collision rates. We find that, for reasonable assumptions of wave amplitude and occurrence rates, the effect of wave-particle interactions on the plasma is equal to or greater than the effect of Coulomb collisions. Thus, wave-particle interactions should not be neglected when modeling the solar wind.

AB - We present a long-duration (∼10 yr) statistical analysis of the temperatures, plasma betas, and temperature ratios for the electron, proton, and alpha-particle populations observed by the Wind spacecraft near 1 au. The mean(median) scalar temperatures are T e,tot = 12.2(11.9) eV, T p,tot = 12.7(8.6) eV, and T α,tot = 23.9(10.8) eV. The mean(median) total plasma betas are β e,tot = 2.31(1.09), β p,tot = 1.79(1.05), and β α,tot = 0.17(0.05). The mean(median) temperature ratios are (T e/T p)tot = 1.64(1.27), (T e/T α)tot = 1.24(0.82), and (T α/T p)tot = 2.50(1.94). We also examined these parameters during time intervals that exclude interplanetary (IP) shocks, times within the magnetic obstacles (MOs) of interplanetary coronal mass ejections (ICMEs), and times that exclude MOs. The only times that show significant alterations to any of the parameters examined are those during MOs. In fact, the only parameter that does not show a significant change during MOs is the electron temperature. Although each parameter shows a broad range of values, the vast majority are near the median. We also compute particle-particle collision rates and compare to effective wave-particle collision rates. We find that, for reasonable assumptions of wave amplitude and occurrence rates, the effect of wave-particle interactions on the plasma is equal to or greater than the effect of Coulomb collisions. Thus, wave-particle interactions should not be neglected when modeling the solar wind.

KW - Sun: coronal mass ejections (CMEs)

KW - plasmas

KW - shock waves

KW - solar wind

UR - http://www.scopus.com/inward/record.url?scp=85051196880&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85051196880&partnerID=8YFLogxK

U2 - 10.3847/1538-4365/aab71c

DO - 10.3847/1538-4365/aab71c

M3 - Article

AN - SCOPUS:85051196880

VL - 236

JO - Astrophysical Journal, Supplement Series

JF - Astrophysical Journal, Supplement Series

SN - 0067-0049

IS - 2

M1 - 41

ER -