On the Momentum Transfer From Polar to Equatorial Ionosphere

Abstract

During space weather events, a large amount of energy and momentum from the solar wind inputs into the ionosphere‐thermosphere. A critical question is that if the solar wind‐magnetosphere interaction drives only the open field region in the polar caps, how the solar wind energy and momentum are transmitted to the low latitude and equatorial ionosphere. This important issue has been studied over decades and is still poorly understood, impeding space weather forecasting ability. Here we use our newly developed 2.5‐D ionosphere‐thermosphere simulation model that self‐consistently solves the density, velocity, and temperature for electrons, multiple ion and neutral species, and electromagnetic fields to study this challenging problem. The focus of the present study is on the prompt response of the ionosphere to a convection disturbance from the polar magnetosphere. The longer time scale responses caused by the neutral winds from the polar caps will be the topic of future studies. We show that the momentum is transferred from polar to equatorial ionosphere predominately by fast magnetosonic waves, and propagation of perturbations from the source region experiences delay, damping, and substantial reflection, and the ionosphere/thermosphere behaves like a low‐band‐pass filter. The finding from this study sheds new insight onto coupling processes within the magnetosphere‐ionosphere system.

Persistence of the Long‐Duration Daytime TEC Enhancements at Different Longitudinal Sectors During the August 2018 Geomagnetic Storm

“…The conventional ionospheric electrodynamics greatly simplifies the physical equations and brings conveniences in studying slow time variations and numerical simulations (Vasyliūnas, 2012). Vasyliūnas's theory is clearly valid in the case of the solar wind and magnetosphere, and it is more rigorous in describing the real physical processes, and it is suitable for wider scope and could be used to deal with the short time scales variations and more detailed physical phenomena (Lotko, 2004; Mannucci, 2018; Song et al, 2009; Tu & Song, 2016, 2019; Tu et al, 2014), though the complex equations could bring large computational burden in numerical simulations. Nevertheless, Vasyliūnas's and the traditional viewpoints give the same quantitative relationship between the electric field and plasma flow, when quasi‐steady equilibrium is satisfied.…”

“… The external source of SW‐M‐I coupling . The external source of SW‐M‐I coupling could also make contribution to the disturbance of vertical drifts during the recovery phase (Song et al, 2009; Tu & Song, 2019; Tu et al, 2008, 2014; Wei et al, 2015). However, in Figure 1, the IMF Bz was small with weak perturbations during 27–30 August, and the Ey was less than 4 mV/m; thus, the disturbed vertical drifts associated with external source are unlikely to produce such strong enhancements. The ionospheric disturbance dynamo effect .…”

“…During geomagnetic storm, the external source from SW-M-I coupling significantly disturbs the plasma drifts and electric field in the middle and low ionosphere (Fejer, 1997;Song et al, 2005Song et al, , 2009Tu & Song, 2019;Tu et al, 2008). This external source is highly correlated with IMF Bz component as well as Ey.…”

Proton Temperature Anisotropy Variations in Inner Heliosphere Estimated with the First Parker Solar Probe Observations

“…With more data in the future, we will be able to better constrain these radial trends. Tu (1988) and Marsch (1991).…”

“…Both regular slow solar wind and Alfvénic slow solar wind show a magnetic moment growing with distance, suggesting that the presence of intense Alfvén waves in the fast wind and the highly Alfvénic slow wind are not solely required for perpendicular heating. (1) indicates Helios results that adapted from Tu (1988) and Marsch (1991).…”