1 Robert Schaefer and Joe Comberiate for the SSUSI Team Robert SchaeferJoe Comberiate (240) (240)

2 Outline  Overview of Products  Algorithm overview  Electron densities  Qeuv and O/N 2  3D Ionosphere product

3 SSUSI low Latitude Product Overview SSUSI Data FileProducts EDR-NIGHT-DISKNmF2, Nadir HmF2 EDR-IONO3D electron densities, ionospheric Bubble properties (centroid location, depth in density drop, volume, orientation to magnetic field), background HmF2, NmF2 EDR-NIGHT-LIMBLimb profile electron densities, NmF2, HmF2 EDR-DAY-DISKO/N 2, Qeuv, TEC, HmF2, NmF2 EDR-DAY-LIMBO/N2, Qeuv, TEC, NmF2, HmF2, NDP (O, O 2, N 2 ) EDR-GAIM-DISKCoarse gridded Radiances designed for GAIM EDR-GAIM-LIMBCoarse gridded Radiances designed for GAIM Avoid using products in red – algorithms need reworking for SSUSI Note: available GUVI products are in green – also neutral density profiles O, O 2, N 2 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 (  SSUSI Data Formats  Described in detail in 3 documents (L1b, SDR, and EDR) format documents  Available from the SSUSI data formats page (  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 a l  Mutual Neutralization – accounted for in nightside limb products O + + O - -> O * + O -> 2 O + hn  Note – F sensitivity is very low and products are less useful

7 O/N 2 and Qeuv  The O/N 2 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   O/N2 takes the ratio of 1356/LBHShort and solar zenith angle as inputs  Qeuv uses O/N 2 and 1356 signal strength as inputs  O/N 2 shows atmospheric heating (O depletion) e.g., 6/17/12 O/N 2 June 16, 2012O/N 2 Hune 17, 2012 SAA

8 3D-IONO Products Ionosphere ProductsBubble Products NeNumber of bubbles Error (Ne)Lat/lon/alt of bubble centroid hmF2 (for each scan)Local time of bubble detection NmF2 (for each scan)Confidence level of bubble detection (%) # of equatorial arc peaksMedian Ne within bubble Equatorial arc peak latitudeStandard deviation of depleted region Ne Equatorial arc peak longitudeMedian Ne uncertainty for bubble region Volume of depleted region Latitudinal span of bubble Orientation of bubble (offset from North) Standard deviation of the alignment difference between bubble and field lines

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

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

11 SSUSI 3D Ionosphere Example: Mar 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 10 6 cm -3 ; 1.12 x 10 6 cm -3

12 The volume of the bubble was 1.25 x 10 8 km 3 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. SSUSI 3D Ionosphere Example: Mar Orbit #17665

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

14 SSUSI Low Latitude Products  SSUSI makes a variety of products for the low latitude regime – e.g., electron densities, bubble characteristics, O/N 2 and Qeuv  Product files organized by (day/night, disk/limb, and 3D ionosphere)  All of these products are available through the SSUSI website   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