CEDAR SSUSI Workshop Low Latitude Products

1. CEDAR SSUSI Workshop Low Latitude Products Robert Schaefer and Joe Comberiate for the SSUSI Team Robert Schaefer Joe Comberiate Robert.Schaefer@jhuapl.eduJoseph.Comberiate@jhuapl.edu (240) 228-2740 (240) 228-3177

2. Outline • Overview of Products • Algorithm overview • Electron densities • Qeuv and O/N2 • 3D Ionosphere product

3. SSUSI low Latitude Product Overview Avoid using products in red – algorithms need reworking for SSUSI Note: available GUVI products are in green – also neutral density profiles O, O2, N2 for GUVI are made with a different algorithm for GUVI and ARE validated. Note in spectrograph mode, GUVI has created a NO emission band product – working on good background subtraction algorithm – but could have NO emission – important for neutral density models

4. SSUSI Product Quality and Validation • Products generally work well when the signals are large, when we are far from the terminator, but there are some exceptions • Products contain Data Quality Indices (DQI) to flag condtions where algorithm may not be working well • DQIs are per pixel bit fields where each bit has a meaning • Defined in the data format document. • By design, bit values are 0=good, 1= bad, so most conservative choice is to use only data where all bits=0 • DQIs bet most issues, but don’t cover every issue - please talk to us before using the products. • SSUSI products go through an official validation (called “CalVal”) funded by the U.S. Air Force • Currently the CalVal for SSUSI F19 will be looking at these derived electron densities and ionospheric bubble quantities – so there may be updates to the algorithms and reprocessed data as a result of that activity • F19 CalVal effort led by Lynette Gelinas, Aerospace

5. SSUSI Description Documents • SSUSI Algorithms • See SSUSI algorithms documents (http://ssusi.jhuapl.edu/data_algorithms) • SSUSI Data Formats • Described in detail in 3 documents (L1b, SDR, and EDR) format documents • Available from the SSUSI data formats page (http://ssusi.jhuapl.edu/data_types) • SSUSI useful Information for Data Usage • Describes most useful variable names • Describes DQI

6. Electron Densities – common technique • Electron densities derived from the 1356 Å radiance • This line is generated by • O* decays by emitting a 1356 Å photon • Radiance measured by SSUSI along the line of sight: • Where we have assumed that the O+ is the dominant ion species in the F region • Some corrections that could include small ~ could be as large as 10-20% • Temperature dependence of al • Mutual Neutralization – accounted for in nightside limb products O+ + O- -> O*+ O -> 2 O + hn • Note – F17 1356 sensitivity is very low and products are less useful

7. O/N2 and Qeuv • The O/N2 and Qeuv parameters are found from lookup tables created with the AURIC model from CPI • Qeuv – a proxy for the solar extreme UV emission energy • http://www.cpi.com/products/auric.html • O/N2 takes the ratio of 1356/LBHShort and solar zenith angle as inputs • Qeuv uses O/N2and 1356 signal strength as inputs • O/N2 shows atmospheric heating (O depletion) e.g., 6/17/12 O/N2 June 16, 2012 O/N2Hune 17, 2012 SAA SAA

8. 3D-IONO Products

9. Observation model for tomographic reconstruction • Portion of ionosphere viewed by successive SSUSI disk scans • Segment of the ionosphere is assumed constant over 10° latitude window, electron density reconstruction reduces to a 2D tomographic inversion problem • A tomographic inversion is performed for each altitude vs. longitude slice, combined to make 3D profile • 3D grid, 1.2 deg lat., 0.33 deg lon., 20 km alt. resolution • Main sources of error • low SNR for counting statistics • limited latitudinal resolution • limited-angle viewing geometry

10. 3D Plasma Bubble Imaging – Visualization Plasma Bubbles Conjugate Footprint Seen From Below Can Identify Equatorial Arcs

11. SSUSI 3D Ionosphere Example: Mar 22 2013 Orbit #17665 • Bubble centroids: (19.2 °N, 10.1 °E), 351 km altitude • (5.6 °S, 16.4 °E), 344 km altitude • Confidence: 94.4% ; 93.0% • Median expected electron density error • 0.96 x 106 cm-3; 1.12 x 106 cm-3

12. SSUSI 3D Ionosphere Example: Mar 22 2013 Orbit #17665 • The volume of the bubble was 1.25 x 108 km3 • Latitudinal depth of the bubble was 18.0° • Bubble was oriented 0.11° away from North and 1.12° away from the magnetic field line.

13. SSUSI 3D Ionosphere Example: Mar 22 2013 Orbit #17665 • Arc peaks at 23.5 °N, 7.6 °S • Can download EDR-IONO files from ssusi.jhuapl.edu

14. SSUSI Low Latitude Products • SSUSI makes a variety of products for the low latitude regime – e.g., electron densities, bubble characteristics, O/N2 and Qeuv • Product files organized by (day/night, disk/limb, and 3D ionosphere) • All of these products are available through the SSUSI website • http://ssusi.jhuapl.edu/data_products • Documentation exists to explain how the products are derived, and how they are formatted. • You are welcome to use SSUSI data – please talk to us before you use it