TY - JOUR
T1 - Temperature of the Polar Inner Heliosheath
T2 - Connection to Solar Activity
AU - Livadiotis, G.
AU - McComas, D. J.
AU - Zirnstein, E. J.
N1 - Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/7/1
Y1 - 2023/7/1
N2 - We study the thermodynamics of the plasma protons in the polar regions of the inner heliosheath (IHS) and its connection with solar activity over solar cycle 24. First, we express the thermodynamic parameters of this plasma with respect to the year of energetic neutral atom (ENA) creation and perform a statistical analysis of temperatures, in order to provide a more precise characterization of the thermodynamics of IHS. Then, we perform an autocorrelation between the IHS temperature and the solar activity, using the proxies of sunspot number and fractional area of the polar coronal holes. We show that there is (i) high correlation between the time series of IHS proton temperatures and sunspot number, which is maximized for a time delay of τ ∼ 2.5 yr for both the north and south polar regions combined; (ii) high negative correlation between the temperature of the proton plasma in the north and south with the coronal hole fractional areas, where the time delay for the two poles combined is τ ∼ 2.71 ± 0.15 yr; and (iii) an asymmetry of a time-delay difference between the poles ∼0.22 yr, indicating that the southern polar ENA source region is ∼19 au closer than the northern one for a solar wind plasma protons of bulk speed of ∼400 km s−1. The findings demonstrate a connection between the IHS thermodynamics and solar activity through the solar wind, primarily manifested by the coronal holes expanding near solar minimum, which drives the expansion of fast solar wind over larger angles from high down to middle latitudes in the IHS.
AB - We study the thermodynamics of the plasma protons in the polar regions of the inner heliosheath (IHS) and its connection with solar activity over solar cycle 24. First, we express the thermodynamic parameters of this plasma with respect to the year of energetic neutral atom (ENA) creation and perform a statistical analysis of temperatures, in order to provide a more precise characterization of the thermodynamics of IHS. Then, we perform an autocorrelation between the IHS temperature and the solar activity, using the proxies of sunspot number and fractional area of the polar coronal holes. We show that there is (i) high correlation between the time series of IHS proton temperatures and sunspot number, which is maximized for a time delay of τ ∼ 2.5 yr for both the north and south polar regions combined; (ii) high negative correlation between the temperature of the proton plasma in the north and south with the coronal hole fractional areas, where the time delay for the two poles combined is τ ∼ 2.71 ± 0.15 yr; and (iii) an asymmetry of a time-delay difference between the poles ∼0.22 yr, indicating that the southern polar ENA source region is ∼19 au closer than the northern one for a solar wind plasma protons of bulk speed of ∼400 km s−1. The findings demonstrate a connection between the IHS thermodynamics and solar activity through the solar wind, primarily manifested by the coronal holes expanding near solar minimum, which drives the expansion of fast solar wind over larger angles from high down to middle latitudes in the IHS.
UR - http://www.scopus.com/inward/record.url?scp=85163925557&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85163925557&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/acd1e1
DO - 10.3847/1538-4357/acd1e1
M3 - Article
AN - SCOPUS:85163925557
SN - 0004-637X
VL - 951
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 21
ER -