GOALS AND OBJECTIVES: THIS PROPOSAL AIMS TO QUANTIFY THE EFFECTS OF LYMAN-ALPHA SOFT X-RAY AND HARD X-RAY SOLAR INPUTS ON THE PRODUCTION OF IONIZATION IN THE D-REGION IONOSPHERE (BELOW 90 KM). IT IS WELL KNOWN THAT LYMAN-ALPHA AND HARD X-RAYS FROM THE SUN PRODUCE IONIZATION IN THE DREGION AND ARE RESPONSIBLE FOR MAINTAINING THE D-REGION DURING THE DAYTIME. LESS UNDERSTOOD IS THE CONTRIBUTION OF SOFT X-RAYS (<10 KEV) DUE TO THE LACK OF OBSERVATIONS OF SOFT X-RAYS FROM SPACE. THE 2017 SOLAR ECLIPSE WILL PROVIDE A UNIQUE OPPORTUNITY TO STUDY THE EFFECTS OF THESE ENERGETIC SOURCES ON D-REGION IONIZATION BY REMOVING AND THEN RE-ESTABLISHING THE SOLAR SOURCES IN A SHORT TIME SPAN AND OVER A LIMITED SPATIAL REGION. MEASUREMENTS OF THE SOURCES FROM SPACE WILL BE CORRELATED WITH D-REGION MEASUREMENTS BEFORE AND AFTER THE ECLIPSE WHILE D-REGION MEASUREMENTS DURING THE ECLIPSE WILL QUANTIFY THE D-REGION IN THE ABSENCE OF THESE SOURCES. DATA: D-REGION IONIZATION MEASUREMENTS WILL BE MADE USING VLF SUBIONOSPHERIC REMOTE SENSING. THE NML (25.2 KHZ) VLF TRANSMITTER IN LAMOURE NORTH DAKOTA WILL BE MONITORED AT A VLF RECEIVER SITE IN BOULDER CO. THIS RECEIVER WILL PROVIDE MEASUREMENTS OF THE VLF AMPLITUDE AND PHASE BEFORE DURING AND AFTER THE ECLIPSE. LYMAN-ALPHA AND EUV OBSERVATIONS FROM SPACE WILL BE PROVIDED BY THE EVE INSTRUMENT ON SDO; SDO IS EXTENDED UNTIL OCTOBER 2017 AT THE EARLIEST. GOES SPACECRAFT PROVIDE HARD X-RAY FLUXES IN THE ENERGY RANGE FROM 1.5 TO 25 KEV. SOFT X-RAYS IN THE RANGE FROM 0.5 TO 6 KEV WILL BE PROVIDED BY THE MINXSS-2 SPACECRAFT WHICH WILL BE LAUNCHED IN JANUARY 2017. HARD X-RAYS UP TO 1 MEV OR HIGHER WILL BE PROVIDED BY THE RHESSI SPACECRAFT. USING THESE SOURCES A COMPLETE SPECTRUM OF IONIZATING RADIATION FROM THE SUN CAN BE ASSEMBLED AND INPUT INTO ATMOSPHERIC CHEMISTRY MODELS. ANALYSIS METHODOLOGY AND MODELING: LYMAN-ALPHA EUV SOFT X-RAY AND HARD X-RAY DATA WILL BE USED TO FORM A COMPLETE PICTURE OF THE SPECTRAL FLUX OF ENERGETIC INPUTS TO THE UPPER ATMOSPHERE FROM THESE SOURCES. ATMOSPHERIC CHEMISTRY MODELING USING THE SOKANKYLA ION CHEMISTRY (SIC) MODEL WILL BE USED TO ASSESS THE EFFECTS OF THESE SOURCES ON D-REGION IONIZATION BEFORE DURING AND AFTER THE ECLIPSE. THE MODEL WILL THEN DETERMINE THE D-REGION ELECTRON AND ION DENSITY PROFILES DURING THE COURSE OF THE ECLIPSE. THE D-REGION IONOSPHERE WILL BE ASSESSED USING A SECOND METHOD IN PARTICULAR USING A PROPAGATION CODE TO SIMULATE THE VLF TRANSMITTER SIGNAL PROPAGATING FROM THE NML TRANSMITTER TO OUR RECEIVER AT BOULDER. THE IONOSPHERE CAN BE SPECIFIED IN 2D ALONG THE PATH. THE PROPAGATION MODEL WAS DEVELOPED BY THE PI; IT IS AN FDTD MODEL CAPABLE OF SIMULATING THE AMPLITUDE AND PHASE OF ANY TRANSMITTER FREQUENCY UP TO HUNDREDS OF KHZ PROPAGATING IN THE EARTH-IONOSPHERE WAVEGUIDE. THE MODELS WILL BE RUN WITH AND WITHOUT AN ECLIPSED REGION TO ASSESS THE DIFFERENCE IN AMPLITUDE AND PHASE OBSERVED WITH AND WITHOUT THE CONTRIBUTIONS OF SOLAR INPUTS. THE MODEL RESULTS WILL THEN BE COMPARED WITH THE OBSERVED AMPLITUDE AND PHASE SIGNALS TO ASSESS THE ACCURACY OF THE MODELS. DIFFERENCES WILL BE STUDIED IN TERMS OF THE ACCURACY OF THE MEASURED SOLAR INPUTS. RELEVANCE: THE PROPOSED WORK CLEARLY CONNECTS THE SOLAR ECLIPSE TO ITS EFFECTS IN THE EARTH S UPPER ATMOSPHERE AND IN PARTICULAR TO THE IONOSPHERETHERMOSPHERE- MESOSPHERE (ITM) SYSTEM. IT DIRECTLY PERTAINS TO THE NATIONAL ACADEMY OF SCIENCE 2013 DECADAL SURVEY IN SOLAR AND SPACE PHYSICS (HELIOPHYSICS) KEY SCIENCE GOAL 2 TO DETERMINE THE DYNAMICS AND COUPLING OF EARTH'S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS.