We present results of global magnetohydrodynamic simulations which reconsider the relationship between the solar wind dynamic pressure (Pd) and magnetopause standoff distance (RSub). We simulate the magnetospheric response to increases in the dynamic pressure by varying separately the solar wind density or velocity for northward and southward interplanetary magnetic field (IMF). We obtain different values of the power law indices N in the relation depending on which parameter, density, or velocity, has been varied and for which IMF orientation. The changes in the standoff distance are smaller (higher N) for a density increase for southward IMF and greater (smaller N) for a velocity increase.
Simple Language Realization
The fresh magnetopause ‘s the boundary between the close-Environment area, that is governed by magnetic job produced in the brand new Earth’s core, and interplanetary area inhabited by the plasma produced regarding the Sunrays known as solar cinch. Contained in this performs, we reexamine the partnership amongst the magnetopause position and you can variables of the latest solar power snap by means of computers modeling. It is found that the dating ranging from solar wind speed and you can thickness and you may magnetopause standing is far more advanced than originally envision.
step 1 Introduction
The magnetopause is one of principal magnetospheric boundaries which separates dense solar wind plasma in the magnetosheath and tenuous and hot magnetospheric plasma. In response to strong solar wind pressure pulses, the magnetopause comes closer to the Earth and geosynchronous spacecraft may exit the magnetosphere and cross the magnetosheath in the subsolar region or even enter into the supersonic solar wind. To date, more than 15 empirical models of the magnetopause have been developed based on a great number of magnetopause crossings under different solar wind conditions (a list of 14 models published by Suvorova & Dmitriev, 2015 ). Chapman and Ferraro ( 1931 ) suggested that the magnetopause location can be determined from the pressure balance condition between the solar wind dynamic pressure (Pd) and the magnetic pressure of the Earth’s dipole. Besides the dynamic pressure, the second important solar wind parameter influencing the magnetopause position is the interplanetary magnetic field (IMF) Bz component (Aubry et al., 1970 ; Fairfield, 1971 ). A strong southward IMF (Bz<0) results in magnetic reconnection at the dayside magnetopause and intensification of the large-scale field-aligned (Region 1) currents connecting the magnetosphere and ionosphere and moving the magnetopause closer to the Earth (Hill & Rassbach, 1975 ; Sibeck, 1994 ). The Pd and Bz are the only two input parameters in several popular magnetopause models (e.g., Petrinec & Russell, 1996 ; Roelof & Sibeck, 1993 ; Shue et al., 1997 ; 1998 ; Sibeck et al., 1991 ). The recent (Lin et al., 2010 ) empirical model replaces the solar wind dynamic pressure by the sum of dynamic and magnetic pressures and takes into account the Earth’s dipole tilt. Moreover, several papers (Dusik et al., 2010 ; Grygorov et al., 2017 ; Merka et al., 2003 ; Samso ) note that the magnetopause significantly expands during radial IMF intervals concluding that the IMF cone angle (the angle between IMF and the Sun-Earth line) eter for calculation of the magnetopause location.
Recently, Nemecek mais aussi al. ( 2016 ) opposed seen magnetopause crossings on Shue http://datingranking.net/pl/geek2geek-recenzja et al. design (Shue ainsi que al., 1997 ) to own half of the final solar years and discovered logical differences amongst the design and you may observations. It debated that the ionospheric conductivity and solar breeze speed is actually a lot more variables you to definitely dictate the fresh new magnetopause standing. The analytical study implies that the typical magnetopause was farther of the world than simply predict during the big date durations which have all the way down conductivity and you can large solar snap velocity. They suggested one intensification away from Ultraviolet light causes a rise on the magnetospheric-ionospheric currents that decreases the magnetized tension within the magnetosphere and you may new magnetopause moves earthward. On the other hand, enhancement of one’s speed intensifies this new viscous correspondence within solar breeze and magnetosphere raising the globally magnetospheric convection and you will taking significantly more magnetized flux toward dayside magnetosphere. We shall mention this type of presumptions less than from the report.