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CEDAR SSUSI Workshop Low Latitude Products

Robert Schaefer and Joe Comberiate

for the SSUSI Team

Robert Schaefer Joe ComberiateRobert.Schaefer@jhuapl.eduJoseph.Comberiate@jhuapl.edu(240) 228-2740 (240) 228-3177

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Outline

Overview of Products Algorithm overview

Electron densities Qeuv and O/N2

3D Ionosphere product

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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

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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

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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

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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

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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

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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

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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

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3D Plasma Bubble Imaging – Visualization

Plasma Bubbles

Conjugate FootprintSeen From Below

Can IdentifyEquatorial Arcs

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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

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• 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

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• 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

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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