SOHO

1. Convection Radial Diffusion Local Acceleration Solar activity drives Ionosphere/Thermosphere and Radiation Belts: Fundamental Sun Solar System Connection Science SOHO Model predictions for the variability (arrows) of I-T temperatures and density versus altitude over the solar cycle (J. Lean, 1997). The predictions must be verified by observations. Similar effects might be anticipated in all planetary atmospheres. Terrestrial I-T measurements in association with coincident EUV observations will determine how the I-T system actually responds to solar EUV variations CRRES observations indicate an abrupt increase in radiation belt fluxes corresponding to the arrival of a solar wind shock. The processes(s) which accelerate the particles to create the belts remain poorly understood, however with two spacecraft, we can track the propagation of shocks that generate new radiation belts TEC O/N2 20 April, 2002 The measurement of the radial gradient of phase space density for fixed adiabatic invariants is the most efficient way to distinguish among various radiation belt acceleration and transport mechanisms. In order to measure these gradients accurately, Radiation Belt Storm Probe (RBSP) mission has two near-equatorial spacecraft in a “chasing” orbit. Three classes of processes can be distinguished by phase space density profiles: large-scale convection; processes which accelerate particles through enhanced radial diffusion; stochastic acceleration process producing local heating. Previous single-point measurements have not been able to identify unambiguously the causal mechanism for radiation belt enhancements. Disturbances driven by solar EUV and Coronal Mass Ejections generate structure in the ionosphere (left: total electron content - red=high) and thermospheric composition (right, O/N2 ratio, red/black = high). Local in-situ measurement of atmospheric parameters is critical to assessing solar EUV and CME effects at mid-latitudes. Two in-situ spacecraft can quantify gradients that are sensed globally with imaging. The variations affect communication, GPS navigation and spacecraft drag. (TEC from Foster, 2004, JPL GPS network data; O/N2 ratio from Polar VIS imager).

2. Living With a Star Geospace MissionOverview • Science Objectives • Characterize and understand the acceleration, global distribution, and variability of energetic electrons and ions in the harsh radiation belt environment: • - Source mechanisms • - Loss mechanisms • - Acceleration, transport and diffusion within the ring current • • Identify and quantify the causes for the ionospheric variations that affect communications, navigation, and radar systems at mid-latitudes: • - Response to solar extreme ultraviolet radiation • - Response to geomagnetic storms • - Sources and characteristics of ionospheric irregularities • • Define the manner by which electric and magnetic fields, currents and plasma connect the inner magnetosphere and ionosphere • Investigation Descriptions • • Radiation Belt Storm Probes - RBSP • - Two spacecraft in nearly identical, low-inclination (<18o, 12o goal), highly elliptical (500 km  5.5 RE) ‘chasing’ orbits separate spatial and temporal variations • • Ionosphere Thermosphere Storm Probes - ITSP • - Two spacecraft in nearly identical, 60-inclination, circular orbits at nominal altitudes of 400 - 450 km employ a range of azimuthal separations to separate spatial and temporal effects • • IonosphereThermosphere imager • - To be launched on a mission of opportunity • Status: • Agency level confirmation of LWS Program and Solar Dynamics Observatory on June 1, 2004 included fully funded Geospace missions with launches in 2010 and 2012. The New Vision for U.S. Space Exploration A major focus of recent NASA scientific efforts has been to understand and predict the causes and the consequences of variations in the Earth’s space environment for the protection of our increasingly technological society. This focus is now broadened to facilitate NASA’s new vision for space exploration, to understand the history of our solar system and to search for habitable environments for life, in the past, present, and future. Major considerations in the generation and habitability of solar system objects and planets are the character of the variable, interplanetary solar system environment driven by the sun, and the nature of the complex interactions that take place between that environment and planetary objects. With the LWS/Geospace Program, Earth is used as a testbed for understanding the responses of all objects in the solar system to solar variability. The platforms from which missions to the Moon and other planets are launched will be developed and reside in low-Earth orbit within Geospace. Astronauts, spacecraft, and instrumentation in these orbits must meet the challenge of the terrestrial radiation belts and South Atlantic anomaly. The LWS/RBSP will provide the observations needed to characterize this radiation environment. Research results will be used to predict intervals of high flux and define requirements for radiation hardening, benefiting not only the space exploration initiative but also our national security and commercial interests. Astronauts and instruments on the lunar surface or in interplanetary space will be exposed to Solar Energetic Particles (SEPs). The LWS/RBSP spacecraft will provide unique multipoint in situ observations that can be used to discriminate between proposed SEP mechanisms and forecast space weather events. By using the Earth’s radiation belts as a laboratory, we will obtain the knowledge needed to understand the environments of other planets and interplanetary space. The results will be used to develop an operational space weather system that safeguards astronauts engaged in space exploration. Forthcoming exploration missions to Mars will employ atmospheric aero-capture and aero-breaking. Observations within the Earth’s ionosphere and thermosphere offer an opportunity to understand and model the atmospheres of Mars and the other planets in our solar system. Because conditions within the Martian atmosphere resemble those within the Earth’s thermosphere, I-TSP observations of the terrestrial thermospheric density, winds, and composition will be used to generate models for application to the Martian atmosphere. Points of contact: David Sibeck (david.g.sibeck@nasa.gov) Nicola Fox (nicola.fox@jhuapl.edu)