Fall meeting of the American Geophysical Union (AGU). Paper on Ionospheric response to the 2009 Sudden Stratospheric Warming

1. Time-dependent three-dimensional
(latitude, longitude, altitude) response of the
ionosphere to the 2009 SSW event
Irfan Azeem, Geoff Crowley, and Adam Reynolds
ASTRA, Boulder, CO
contact: iazeem@astraspace.net
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2. Outline
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Introduction
2009 SSW Event
Motivation
IDA4D Assimilation Algorithm
Assimilation Results: 2009 SSW
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TEC
Electron Density
Conclusions
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3. Introduction
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Sudden Stratospheric Warming (SSW) events are dramatic
meteorological phenomena occurring in the winter
stratosphere during which the polar vortex becomes highly
distorted or breaks down (splits), accompanied by disruptions
in the westerly mean circulation in a rather abrupt manner.
SSWs are an important manifestation of vertical dynamical
coupling in the atmosphere.
The key mechanism by Matsuno (1971) is now widely
accepted: the growth of upward propagating planetary waves
from the troposphere and their interaction with the mean
flow.
Modeling and experimental studies have shown the impact of
SSW on MLT region (Myrabo et. al., 1984; Matveeva &
Semenov, 1985; Walterscheid, 2000; Sigernes et al., 2003,
Azeem et al., 2007, 2009).
SA21C, Fall AG 2013
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4. NCEP
2009 SSW Event
http://acd-ext.gsfc.nasa.gov/Data_services/met/ann_data.html
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5. Motivation
RESULTS
TEC response at 75W during the
2009 SSW event show a distint
local time dependency.
8-10 LT: TEC increase
16-18 LT: TEC decrease
Ionospheric changes in the American sector during Goncharenko et al. [2010].
the 2009 SSW event. Top panels show quiet-time
averages while bottom panels show TEC observations
for January 27 2009. Goncharenko et al. [2010].
Q. What is the global response of the ionosphere to dynamical forcing
spawned during SSW events?
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6. IDE TEC
(a) January 20, 2009.
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IDE TEC
IDE TEC
(b) January 24, 2009.
(c) January 27, 2009.

7. IDA4D Assimilation


The global IDA4D images of the ionosphere will allow us to
characterize, unambiguously, the ionospheric global response
to SSW events at different heights, latitude regions and
longitude sectors as a function of time.

IDA4D will allow us to compare and contrast how the
ionosphere responds to different SSW events and how it
recovers from the SSW stimulated state.

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Ionospheric Data Assimilation Four-Dimensional (IDA4D)
algorithm [Bust et al., 2004]
IDA4D provides three-dimensional maps of the global
distribution of the ionospheric electron density and other
plasma parameters (e.g. hmF2, foF2, NmF2, TEC), as a function
of time.
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8. Data Sources
Typical data sources used by IDA4D include:
1. Ground-based GPS slant total electron content (TEC)
2. Ground-based digisonde and incoherent scatter radar
3. Ground-based DORIS tx and ~4 low earth orbit satellites with DORIS rx
4. Space-based GPS occultation measurements of TEC
5. Space-based topside GPS TEC
6. Space-based in-situ electron density (DMSP)
7. Space-based UV airglow derived electron density (GUVI/SSUSI)
• Orange dots: 350 km IPP of ground-based
GPS
• Red squares: Ground DORIS transmitters
• Red lines: 350 km intercept to the
satellite from DORIS transmitters
• Solid yellow lines: GPSRO traces
• Dashed yellow lines: Topside TEC
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9. TEC Response
15 UT

15 UT
9

TEC change during the 2009 SSW
event

Typical day-to-day variability in TEC
TEC enhancement in the South
American Sector
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10. TEC Response
21 UT

21 UT
10

TEC change during the 2009 SSW
event

Typical day-to-day variability in TEC
TEC suppression in the South
American Sector
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11. 

Their study was limited to locations where GPS data was
readily available, so that over large swaths of the globe
they were unable to characterize the ionosphere.

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IDA4D results confirms the observed ionopsheric
changes reported by Goncharenko et al. [2010].
In this study we extend previous studies and examine
the global response of the ionosphere to SSWs using the
IDA4D assimilative model.
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12. Avg. Day to Day
TEC Variability
UT = 00
UT = 03
UT = 06
UT = 09
UT = 12
UT = 15
UT = 18
UT = 21
DTEC
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13. First EOF:
TEC Response on Jan. 26
UT = 00
UT = 06
UT = 09
UT = 12
13
UT = 03
UT = 15
UT = 18
UT = 21
DTEC

14. First EOF:
TEC Response on Jan. 27
UT = 00
UT = 06
UT = 09
UT = 12
14
UT = 03
UT = 15
UT = 18
UT = 21
DTEC

15. First EOF:
TEC Response on Jan. 28
UT = 00
UT = 06
UT = 09
UT = 12
15
UT = 03
UT = 15
UT = 18
UT = 21
DTEC

16. First EOF:
TEC Response on Feb. 1
UT = 00
UT = 06
UT = 09
UT = 12
16
UT = 03
UT = 15
UT = 18
UT = 21
DTEC

17. NE Response
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Increased upward drifts due to dynamo electric field
Plasma is lifted to higher altitudes
Fejer et al. 2010 JGR
Slower recombination
Increase in plasma density
EIA fed by this plasma
Goncharenko et al. 2010 GRL
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18. NE Response
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
American Sector
Jan 22, Jan 27, and Feb 7, 2009
PRE SSW
Ne
increase
SSW
POST SSW
18
electrons/m3
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19. NE Response
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
Asia Pacific Sector
Jan 22, Jan 27, and Feb 7, 2009
PRE SSW
Ne
decrease
SSW
POST SSW
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electrons/m3
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20. Conclusions


IDA4D assimilation algorithm used to study global
response of the ionosphere to the 2009 SSW event.
IDA4D captures salient features of TEC perturbations in
the American sector previously reported by Goncharenko
et al. [2010].

New findings:



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10 TECU decrease in ionospheric TEC in Asia Pacific sector.
American Sector: Plasma density increase in the Appleton
Anomaly region. Also, the Southern Hemisphere peak is lifted
up at the onset of the SSW event.
Asia Pacific Sector: Plasma density decrease in the Appleton
Anomaly region.
SA21C, Fall AG 2013
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