Energy Transfer Across the Magnetopause Under Radial IMF Conditions

Abstract

A global MHD model is used to study the energy transfer from solar wind to magnetosphere through magnetopause under radial interplanetary magnetic fields (IMFs). We use the streamline method to determine the smooth surface of the magnetopause by searching the inner boundary of the solar-wind streamline and discuss the roles of magnetic reconnection and viscous interaction under radial IMFs, which we compare with cases of north–south IMFs. We find that (1) the energy transfer across the magnetopause is asymmetric between the northern and southern hemispheres due to different reconnection locations, particularly for electromagnetic energy; (2) for sunward IMF, the most significant area of the net input of mechanical energy occurs on the day side and near-Earth magnetotail, and the electromagnetic energy input in the northern hemisphere is much larger than in the southern hemisphere on the night side; (3) the mechanical and electromagnetic energy-transfer distribution in the northern (southern) hemisphere for earthward IMF is the same as that in the southern (northern) hemisphere for sunward IMF; (4) the electromagnetic energy input for radial IMF is two times larger than for northward IMF, but three times smaller than for southward IMF, the viscous effect is smaller than for northward IMF but comparable to that for southward IMF, the rate of energy transfer is 2.22% for radial IMF, which is lower than 4.95% for southward IMF, but higher than 1.7% for northward IMF; and (5) the Akasofu-type energy-coupling formula, ϵ, is not suitable for the solar-wind events dominated by IMF B x .

HMB Variations Measured by SuperDARN During the Extremely Radial IMFs: Is the Coupling Function Applicable in Radial IMF?

“…Our statistical results are consistent with the Figure 9 within Juusola et al (2014) for the difference in field-aligned current (FAC) during the antisunward and sunward direction of radial IMF. Lu et al (2021) have discussed that radial IMF leads to a north-south asymmetry of the magnetopause boundary layers (in simple terms, similar to Figure 7), which is responsible for the difference between sunward and antisunward IMF groups.…”

“…In their findings, the magnitudes of CPCP and FAC for radial IMFs are both between the corresponding magnitudes during southward and northward IMFs. Besides, Lu et al (2021) have found that the mechanical energy inputs in radial, southward, and northward IMFs are roughly comparable by the SWMF model. And the electromagnetic energy input in radial IMF is 2 times larger than that in northward IMF, but three times smaller than that in southward IMF.…”

“…Lu et al. (2021) have discussed that radial IMF leads to a north‐south asymmetry of the magnetopause boundary layers (in simple terms, similar to Figure 7), which is responsible for the difference between sunward and antisunward IMF groups.…”

“…Besides, Lu et al. (2021) have found that the mechanical energy inputs in radial, southward, and northward IMFs are roughly comparable by the SWMF model. And the electromagnetic energy input in radial IMF is 2 times larger than that in northward IMF, but three times smaller than that in southward IMF.…”

A magnetohydrodynamic simulation of the dayside magnetic reconnection between the solar wind and the Martian crustal field

“…At the Earth, which has a global dipole magnetic field, it is sug- gested that under the radial IMF condition, the kinetic processes upstream of the bow shock can deflect solar wind flow, which results in the smaller strength and greater turbulence of the magnetic field in the magnetosheath, along with a weaker pressure imposed on the magnetopause (e.g., Engebretson et al 1991;Lin et al 1991;Samsonov et al 2012). The locations of the magnetopause and bow shock, and the energy transfer across the magnetopause are also influenced by the radial IMFs (e.g., Dušík et al 2010;Wang et al 2020a;Lu et al 2021). For Venus, which has no intrinsic magnetic field, but has an ionosphere and an induced magnetosphere, it is reported that by providing an additional driver, the magnetic tension pointing outward from Venus can force the magnetosheath plasma to flow faster in the azimuthal direction around Venus, while decelerating the upstream plasma in the X direction (e.g., Chang et al 2020).…”