Abstract
<strong class="journal-contentHeaderColor">Abstract.</strong> Solar wind forcing, e.g., interplanetary shock and/or solar wind dynamic pressure pulses impacting Earth's magnetosphere, manifests many fundamental important space physics phenomena, including producing electromagnetic waves, plasma heating, and energetic particle acceleration. This paper summarizes our present understanding of the magnetospheric response to solar wind forcing in the aspects of radiation belt electrons, ring current ions and plasmaspheric plasma physics based on in situ spacecraft measurements, ground-based magnetometer data, magnetohydrodynamics (MHD) and kinetic simulations. Magnetosphere response to solar wind forcing is not just a âone-kickâ scenario. It is found that after the impact of solar wind forcing on Earth's magnetosphere, plasma heating and energetic particle acceleration started nearly immediately and could last for a few hours. Even a small dynamic pressure change in interplanetary shock or solar wind pressure pulse can play a non-negligible role in magnetospheric physics. The impact leads to generation of a series of waves, including poloidal-mode ultra-low-frequency (ULF) waves. The fast acceleration of energetic electrons in the radiation belt and energetic ions in the ring current region response to the impact usually contains two contributing steps: (1)Â the initial adiabatic acceleration due to the magnetospheric compression, (2)Â followed by the waveâparticle resonant acceleration dominated by global or localized poloidal ULF waves excited at various <span class="inline-formula"><i>L</i></span>-shells. Generalized theory of drift and driftâbounce resonance with growth- or decay-localized ULF waves has been developed to explain in situ spacecraft observations. The wave-related observational features like distorted energy spectrum, âboomerangâ and âfishboneâ pitch angle distributions of radiation belt electrons, ring current ions and plasmaspheric plasma can be explained in the framework of this generalized theory. It is worth pointing out here that poloidal ULF waves are much more efficient at accelerating and modulating electrons (fundamental mode) in the radiation belt and charged ions (second harmonic) in the ring current region. The results presented in this paper can be widely used in solar wind interacting with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune and other astrophysical objects with magnetic fields.
Highlights
Even a small dynamic pressure change of interplanetary shock or solar wind pressure pulse can play a non-negligible role in magnetospheric physics
The sudden changes of charged particle fluxes in the inner magnetosphere including both relativistic electrons in the radiation belt [Arnoldy 1982, Blake et al, 1992, Li et al, 1993, Hudson et al, 1994, Tan et al, 2004, Zong et al, 2009, Hao et al, 2019] and energetic ions [Zong et al, 2012,l 2017; Ren et al 2016, 2017a] in the ring current region are noted to be closely related to Storm Sudden Commencement" (SSC) caused by the interplanetary shock impacting on the Earth’s magnetosphere
These results suggest that a significant portion of energetic charged particles in the ring current and radiation belt and region could be produced even before the build-up of the enhanced ring current which produces the magnetic storm
Summary
Hannes Alfvén Medal to me for the year 2020, I feel deeply honored and very happy to obtain so much recognition for my work, because Hannes Alfvén was one of the giants in space physics and astrophysics, and one of my heroes. While few people know that Hannes Alfvén can speak some Chinese (Fig. 1) besides Swedish and English as indicated by Wikipedia He has visited China twice, his first visit was invited by Prof. Jeoujang Jaw who is the founder of Chinese space program [Zhang &Yin, 2018] During his in total of 50 days’ visiting in China, Hannes Alfvén has given a number of lectures and promoted China’s space physics. As a student majored in space science, I first studied Alfvén’s eminent works - the motion of charged particles (Alfvén and Fälthammar, 1963) and ‘Existence of Electromagnetic–Hydrodynamic Waves’ (Alfvén, 1942). The latter one is named after him as Alfvén waves. It is understood that 55 Alfvén waves are ubiquitous and of fundamental importance in plasma physics, space physics & astrophysics, they occur in planetary magnetospheres, in laboratory plasma, in stellar coronas and winds, and many other astrophysical plasmas in the universe
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