Abstract
The Earth’s magnetosphere is region that is carved out by the solar wind as it flows past and interacts with the terrestrial magnetic field. The inner magnetosphere is the region that contains the plasmasphere, ring current, and the radiation belts all co-located within about 6.6 Re, nominally taken to be bounding this region. This region is highly dynamic and is home to a variety of plasma waves and particle populations ranging in energy from a few eV to relativistic and ultra-relativistic electrons and ions. The interplanetary magnetic field (IMF) embedded in the solar wind via the process of magnetic reconnection at the sub-solar point sets up plasma convection and creates the magnetotail. Magnetic reconnection also occurs in the tail and is responsible for explosive phenomena known as substorms. Substorms inject low-energy particles into the inner magnetosphere and help generate and sustain plasma waves. Transients in the solar wind such as coronal mass ejections (CMEs), co-rotating interaction regions (CIRs), and interplanetary shocks compress the magnetosphere resulting in geomagnetic storms, energization, and loss of energetic electrons in the outer radiation belt nad enhance the ring current, thereby driving the geomagnetic dynamics. The Specification and Prediction of the Coupled Inner-Magnetospheric Environment (SPeCIMEN) is one of the four elements of VarSITI (Variability of the Sun and Its Terrestrial Impact) program which seeks to quantitatively predict and specify the inner magnetospheric environment based on Sun/solar wind driving inputs. During the past 4 years, the SPeCIMEN project has brought together scientists and researchers from across the world and facilitated their efforts to achieve the project goal. This review provides an overview of some of the significant scientific advances in understanding the dynamical processes and their interconnectedness during the VarSITI era. Major space missions, with instrument suites providing in situ measurements, ground-based programs, progress in theory, and modeling are briefly discussed. Open outstanding questions and future directions of inner magnetospheric research are explored.
Highlights
The term “magnetosphere” was introduced by Gold in 1959 (Gold 1959) to describe the region above the ionosphere and coincided with James Van Allen’s discovery of the radiation belts (Van Allen et al 1959)
The outer belt is populated mostly by electrons ranging in energy from a few hundred keV to tens of MeV and is highly dynamical in nature varying on time scales ranging from minutes to years (Baker and Kanekal 2008)
In the recent past major missions such as NASA’s Van Allen Probes (Mauk et al 2014; Sibeck et al 2012), Japan Aerospace eXploration Agency (JAXA)’s Arase (Miyoshi et al 2018), THEMIS (Angelopoulos 2008), and others vastly improved our understanding of the magnetosphere, the inner magnetosphere which includes the radiation belts and the plasmasphere
Summary
The term “magnetosphere” was introduced by Gold in 1959 (Gold 1959) to describe the region above the ionosphere and coincided with James Van Allen’s discovery of the radiation belts (Van Allen et al 1959). In the recent past major missions such as NASA’s Van Allen Probes (Mauk et al 2014; Sibeck et al 2012), JAXA’s Arase (Miyoshi et al 2018), THEMIS (Angelopoulos 2008), and others vastly improved our understanding of the magnetosphere, the inner magnetosphere which includes the radiation belts and the plasmasphere. New observations such as the discovery of a long-term storage ring or the “third belt” (Baker et al 2013) to the first direct observation of wave-particle interaction (Fennell et al 2014; Kurita et al 2018; Kasahara et al 2018) are prime examples of new observational in situ measurements enabled by advances in instrumentation. The time scales of magnetospheric response, the inner magnetosphere, range from minutes to years (Baker and Kanekal 2008)
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