1 Robert Schaefer and Joe Comberiate for the SSUSI Team Robert SchaeferJoe Comberiate...
-
Upload
mavis-stafford -
Category
Documents
-
view
213 -
download
0
Transcript of 1 Robert Schaefer and Joe Comberiate for the SSUSI Team Robert SchaeferJoe Comberiate...
1
CEDAR SSUSI Workshop Low Latitude Products
Robert Schaefer and Joe Comberiate
for the SSUSI Team
Robert Schaefer Joe [email protected]@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
SSUSI Data File Products
EDR-NIGHT-DISK NmF2, Nadir HmF2
EDR-IONO 3D electron densities, ionospheric Bubble properties (centroid location, depth in density drop, volume, orientation to magnetic field), background HmF2, NmF2
EDR-NIGHT-LIMB Limb profile electron densities, NmF2, HmF2
EDR-DAY-DISK O/N2, Qeuv, TEC, HmF2, NmF2
EDR-DAY-LIMB O/N2, Qeuv, TEC, NmF2, HmF2, NDP (O, O2, N2)
EDR-GAIM-DISK Coarse gridded Radiances designed for GAIM
EDR-GAIM-LIMB Coarse 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, 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/N2 and 1356 signal strength as inputs
O/N2 shows atmospheric heating (O depletion) e.g., 6/17/12
O/N2 June 16, 2012 O/N2 Hune 17, 2012
SAA SAA
8
3D-IONO ProductsIonosphere Products Bubble Products
Ne Number 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 peaks Median Ne within bubble
Equatorial arc peak latitude Standard deviation of depleted region Ne
Equatorial arc peak longitude Median 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
1010
3D Plasma Bubble Imaging – Visualization
Plasma Bubbles
Conjugate FootprintSeen From Below
Can IdentifyEquatorial 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
• 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.
SSUSI 3D Ionosphere Example: Mar 22 2013 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 22 2013 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/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