Abstract
The Sun’s connection with the Earth’s magnetic field and atmosphere is carried out through the exchange of electromagnetic and mass flux and is regulated by a complex interconnection of processes. During space weather events, solar flares or fast streams of solar atmosphere strongly disturb the Earth’s environment. Often the electric currents that connect the different parts of the Sun-Earth system become unstable and explosively release the stored electromagnetic energy in one of the more dramatic expressions of space weather – the auroral storm and substorm. Some aspects of the magnetosphere-ionosphere connection that generates auroral arcs during space weather events are well-known. However, several fundamental problems remain unsolved because of the lack of unambiguous identification of the magnetic field connection between the magnetosphere and the ionosphere. The correct mapping between different regions of the magnetosphere and their foot-points in the ionosphere, coupled with appropriate distributed measurements of plasma and fields in focused regions of the magnetosphere, is necessary to establish unambiguously that a given magnetospheric process is the generator of an observed arc. The three most important problems for which the correct magnetic field mapping would provide closure to are the substorm growth phase arcs, the expansion phase onset arcs and the system of arcs that emerge from the magnetosphere-ionosphere connection during the development of the early substorm expansion phase phenomenon known as substorm current wedge (SCW). Energetic electron beams, used as magnetic field tracers, can enable the closure needed. However, the application of beams as tracers require demonstration that the beams can be injected into the loss cone, that the spacecraft potentials induced by the beam emission are manageable, and that sufficient electron flux reaches the atmosphere to be detectable by optical or radio means after the beam has propagated thousands of kilometers under competing effects of beam spread and constriction as well as effects of beam-induced instabilities. In this communication we provide a review of the latest results of synergistic research carried out under the NSF INSPIRE program to address these challenges and discuss the next steps toward the realization of active experiments in space using relativistic electron beams.
Highlights
The Sun and the Earth are coupled in multiple ways
Recent efforts to couple models of ion drift physics in the inner magnetosphere to MHD models of the outer magnetosphere (De Zeeuw et al, 2004; Pembroke et al, 2012) reveal new structure and dynamics in the magnetotail; the same efforts underline inherent complexity in the magnetic-field topology. This communication describes how unambiguous magnetic field mapping can be achieved by firing a beam of high-energy electrons from the source region into the ionosphere
The new simulation results show that the peak of the energy deposition from a sequence of 20 pulses spanning 100 ms and totaling 100 J, or a sequence of 200 pulses spanning 1 second and totaling 1 kJ, occurs slightly below 60 km altitude, in the atmospheric region known as the D-region, and that approximately 2.2% of the total injected energy is converted to N2 1P emissions, and 0.6% is converted to N+2 1N emissions
Summary
The Sun and the Earth are coupled in multiple ways. Heat coming from the Sun is the main energy source of Earth’s weather. Solar flares or fast streams of solar wind strongly disturb the Earth’s surrounding environment known as the magnetosphere Often during these events the electric currents that connect the different parts of the Earth’s magnetosphere with the ionosphere become unstable and explosively release the stored electromagnetic and particle energy in one of the more dramatic expressions of space weather—geomagnetic storms and substorms (e.g., Gonzalez et al, 1994). These phenomena deposit large fluxes of energetic charged particles and electromagnetic energy into the atmosphere, driving the bright dynamic optical auroral displays. The three most important questions for which the correct magnetic field mapping would provide closure to are: How are the substorm growth phase arcs generated, how are the expansion phase onset arcs generated and how does the system of arcs and electric currents known as substorm current wedge (SCW; e.g., McPherron et al, 1973; Pytte et al, 1976) emerge during the early substorm expansion phase
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