We present a study of all shocks observed from Pioneers and Voyagers in 1973–1982. The average shock strength increases with the heliocentric distance outside 1 AU, reaches a maximum near 5 AU, and then decreases with the distance. The increase in the entropy of the solar wind protons across shocks also reaches a maximum near 5 AU. When an average shock propagates through the solar wind, the shock heating increases the entropy of the solar wind protons by approximately 0.8×0−23 J/K/proton. We also use plasma data from Voyagers and Pioneers between 1 and 30 AU and data from IMP at 1 AU to calculate the increase in the average entropy of solar wind protons with the heliocentric distance. When the distance increases by a factor of 10, the entropy increases by about 4×10−23 J/K/proton. In order to evaluate the role played by shocks for the heating of the solar wind, we use a MHD simulation model to calculate the entropy changes for the November, 1977 event. Shock heating is the only heating mechanism included in the model. The calculated entropy increase agrees reasonably well with that calculated from observational data. The simulation result suggests that shocks are chiefly responsible for the heating of the solar wind plasma between 1 and 15 AU.
The solar wind‐magnetosphere coupling is investigated in terms of forty‐three moderate and intense storms (Dst <‐50 nT) and the associated southward IMF events during 1972 to 1982. The solar wind data is taken from spacecraft IMP‐8 and the geomagnetic storms are described by Dst and AE. The results show that: (1) There are 11 events (25.6% of the total 43 events) which closely follow a shock, 18 events (42%) which occur in the downstream of a shock, and the remainder 14 events bear no relation to the interplanetary shocks. Most of these events are accompanied with the increase of the magnetic field intensity and the dynamic pressure of the solar wind; (2) Only substorms exist when the interplanetary dawn‐to‐dusk electric field EI is less than 4 mV/m, but both of magnetic storms and substorms occur simultaneously if the EI is greater than 5 mV/m; (3) The ring current energization is related to the dynamic pressure (ρV 2), rather than the density or the velocity alone; (4) While the southward IMF component BZ is crucial, the relative strength of BX,BY to the BZ also play a certain role in the energy transfer from the solar wind to the magnetosphere. The energy coupling between the solar wind and the magnetosphere is enhanced if the relative strength is larger.
Three flux transfer events (FTEs) were detected in magnetosheath near the south cusp of the dawn side by Cluster II during the interval from 11:00 to 11:15UT on March 2nd, 2001. In this paper, we analyze the magnetic morphology and the plasma characteristics of these events using the magnetic field and plasma data observed by the four spacecrafts of Cluster II as well as the electric current density in the region Cluster II passed. The results show that the magnetic reconnection at the dayside magnetopause can occur near the cusp when the IMF BY component is dominant. The difference of p+B2/8τ (the sum of magnetic and plasma pressure) measured inside and outside the events may not be balanced with the tension of the helical magnetic field at the initial stage when a flux tube is forming, and it needs a growing time to reach an equilibrium. The size of the section of the FTEs flux tubes in L‐M plane is about 1.89RE. There are not only axis‐aligned current inside the flux tubes but also annular current, and the axis‐aligned current flows basically along the axis‐aligned magnetic field.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.