Preparing for the Living With a Star Ionosphere-Thermosphere Storm Probe I Mission I
Presiding: J M Grebowsky, NASA Goddard Space Flight Center; J ( Yee, Applied Physics Laboratory, Johns Hopkins University
SA13B-01 INVITED 13:33h
The Ionospheric-Thermospheric Component of the LWS-Geospace Program
The Geospace Mission Definition Team report made a persuasive case for investigating the ionosphere-thermosphere system with both LEO in situ instruments and GEO ionospheric imaging. The GMDT science objectives were derived from the Living With a Star Science Architecture Team's consideration of space weather effects that concern society. The two highest priority ionospheric objectives are "Determine the effects of the long and short term variability of the Sun on the global-scale behavior of the ionospheric electron density" and "Determine the solar and geospace causes of small scale density irregularities in the 100-1000 km altitude range". These general objectives were then focused on specific science questions such as "How does the ionosphere-thermosphere system vary in response to changing fluxes of solar extreme ultraviolet radiation?", How does the mid- and low-latitude ionosphere-thermosphere system respond to geomagnetic storms?", and "What are the sources and characteristics of ionospheric irregularities at mid-latitudes?". Since the submission of the GMDT report to NASA, the case for investigating the disturbed mid-latitude ionosphere has become even more compelling. Society has become more vulnerable to ionospheric storms through augmented GPS systems for aviation. The ionospheric response to geomagnetic storms has been shown to extend from the equator through mid-latitudes and across the polar caps and from the F region to the equatorial plane. The total electron content from the peak of the positive-phase to the minima of the negative phase varies by up to one order of magnitude. Simulations have demonstrated that thermospheric transport can carry disturbed O/N2 ratios from the auroral zone to the equator. Density irregularities have been discovered with scale lengths of 100 km to the GPS signal Fresnel length (~ 400m). The GMDT developed a strategy to characterize and understand these phenomena. At low altitudes, within the thermosphere, two Ionospheric-Thermospheric Storm Probes were proposed with in situ instruments. The two ITSP will enable the separation of temporal from spatial phenomena and the investigation of temporal phenomena with time scales less than the orbital period. At high altitude a GEO ionospheric imager will yield context by providing global picture of the ionospheric-thermospheric response and evolution during solar disturbances and geomagnetic storms.
SA13B-02 INVITED 13:51h
The C/NOFS Satellite and its Relation to the Space Weather Objectives of NASA's Living With a Star Program
A major objective of NASA's Living With a Star mission is to understand the variability of the plasma density in the earth's low and mid latitude ionosphere, including the conditions leading to the formation of equatorial spread-F irregularities and their location, magnitude, and spatial and temporal evolution. The main objectives of the Air Force Communication / Navigation Outage Forecasting System (C/NOFS) Mission of the Air Force Research Laboratory are to understand, model, and forecast the presence of equatorial ionospheric irregularities that adversely impact communication and navigation systems. Thus, the C/NOFS mission objectives are directly compatible with fundamental space weather goals of the LWS geospace program. The C/NOFS mission includes a satellite scheduled to be launched in September, 2005 into a low inclination (13°) elliptical (~375 x 710 km) orbit, as well as extensive ground-based observations and theory and modeling activities. The first satellite solely dedicated to forecasting ionospheric irregularities and radio wave scintillations, C/NOFS is equipped with sensors that measure ambient and fluctuating electron densities; ion and electron temperatures; AC and DC electric fields; magnetic fields; neutral winds; ion drifts; optical lightning emissions; ionospheric scintillations; and the electron content along the lines of sight between C/NOFS, GPS satellites, and ground receiver sites. To our knowledge, the sensor suite on C/NOFS is richer than on any previously flown equatorial satellite. C/NOFS is a joint Air Force Research Lab (AFRL) and Space Test Program (STP) mission. The neutral wind meter and ion drift meter are provided as part of the UTD Coupled-Ionosphere-Neutral Dynamics Investigation (CINDI) package that is funded by NASA's Explorer Program. This talk presents an overview of the C/NOFS mission and discusses its relevance to the LWS Geospace I-T Storm Probe mission.
SA13B-03 INVITED 14:09h
Challenges in Modeling the Mid-latitude Thermosphere-Ionosphere Response to Geomagnetic Storms
Modeling, predicting, and understanding the physics of the response of the mid-latitude thermosphere-ionosphere to geomagnetic storms is one of the primary goals of the LWS I-T Storm Probes. The response is complex due to the myriad of processes not only in the coupling of the ionosphere to the inner magnetosphere, but also within the upper atmosphere itself, where neutral-plasma interactions are clearly evident. Electrodynamic coupling between the inner magnetosphere and ionosphere encroach on the mid-latitudes from both sides. From the high latitude side, sub-auroral polarization electric fields transport and erode plasma, creating storm enhanced densities and expanding trough features equatorward. From the low latitudes, penetration electric fields redistribute plasma, moving the equatorial ionization anomaly peaks many degrees poleward. Injection of energy and momentum from the magnetosphere also drives wind surges and restructures the global circulation. Neutral composition changes follow, spreading equatorward often with distinct longitude dependence. Neutral wind and composition changes combine with the electrodynamic drift to enhance, deplete, and restructure the plasma, producing at times extreme longitude dependence. Although some of these effects can be modeled generically, many of the features are still elusive and have yet to be understood or modeled in a realistic way.
SA13B-04 14:27h
Understanding the ionosphere-thermosphere system through modeling and data assimilation
The ionosphere and thermosphere constitute an important part of near Earth space environment where low-Earth orbiting satellites operate and through which communication and navigation signals are being transmitted. The ionosphere-thermosphere system is, however, subject to several geophysical forcings originating from the Sun. The interaction between the solar wind and the Earth's magnetosphere results in a fraction of the solar wind energy and plasma being transmitted into the magnetosphere, and subsequently into the ionosphere and thermosphere to produce auroras and other geomagnetic phenomena. Solar energetic particles penetrate into the upper and middle atmosphere to cause significant ionization and chemical effects. Solar UV and EUV radiation is the main source of energy for heating, ionization, and photochemical reactions in the thermosphere and ionosphere. The LWS' Ionosphere-Thermosphere Storm Probe (ITSP) mission is designated to monitor the variability of the ionosphere-thermosphere system in response to these geophysical forcings. The Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure and the Thermosphere-Ionosphere-Mesosphere Electrodynamics General Circulation Model (TIME-GCM) are well suited to contribute to the scientific objectives of the ITSP mission. In this talk we will discuss the capabilities of AMIE and TIME-GCM, and jointly, how they can provide a better understanding of the impact of various external forcings on the ionosphere-thermosphere system.
SA13B-05 INVITED 14:42h
GUVI Observations of Solar EUV and Geomagnetic Storm Control of the Ionosphere and Thermosphere
The mid-latitude thermosphere and ionosphere are influenced by both the equatorial processes and the polar inputs. With the current baseline configuration of Living With a Star satellites combined with a geosynchronous imager we have a powerful tool for examining the processes at work in the IT. In this talk we will describe how we can prepare for the era of the IT Storm probes and what we will be able to investigate. We are able to delineate science questions and suggest satellite configurations based on our experience with the TIMED GUVI instrument and the work we've carried out using IMAGE, Polar, DMSP, and ROCSat data. One of the most important lessons to be learned is that, while the science return will be greater if the IT probes and the Geospace imageer fly contemporaneously, we can still increase our knowledge of the physics and climatology of the IT system at all latitudes when we finally see the Storm Probes fly. The Storm Probes will fly in a data and model rich environment. We will discuss the tools available for integrating data and models and where the gaps lie in the current implementation. To ground this in reality we will show examples of data and model comparisons and indicate where the missing inputs are and what we can do to improve our understanding of the physics of the IT region. These data will include observations of the IT during quiet and disturbed times as well as during and after solar flares.