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

SA21C, Fall AG 20131 04/12/2023

Outline

● Introduction● 2009 SSW Event● Motivation● IDA4D Assimilation Algorithm● Assimilation Results: 2009 SSW

● TEC● Electron Density

● Conclusions

04/12/20232 SA21C, Fall AG 2013

Introduction

● 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). 04/12/20233 SA21C, Fall AG 2013

2009 SSW Event

http://acd-ext.gsfc.nasa.gov/Data_services/met/ann_data.html

NC

EP

04/12/20234 SA21C, Fall AG 2013

RESULTSMotivation

Ionospheric changes in the American sector during the 2009 SSW event. Top panels show quiet-time averages while bottom panels show TEC observations for January 27 2009. Goncharenko et al. [2010].

TEC response at 75W during the 2009 SSW event show a distint local time dependency.

8-10 LT: TEC increase

16-18 LT: TEC decrease

Goncharenko et al. [2010].

Q. What is the global response of the ionosphere to dynamical forcing spawned during SSW events?

04/12/20235 SA21C, Fall AG 2013

IDE TEC IDE TEC

(a) January 20, 2009. (b) January 24, 2009.

(c) January 27, 2009.

IDE TEC

6

· Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm [Bust et al., 2004]

· 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.

· 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.

IDA4D Assimilation

04/12/20237 SA21C, Fall AG 2013

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 radar3. Ground-based DORIS tx and ~4 low earth orbit satellites with DORIS rx4. Space-based GPS occultation measurements of TEC5. Space-based topside GPS TEC6. 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

04/12/20238 SA21C, Fall AG 2013

TEC Response

· Typical day-to-day variability in TEC · TEC change during the 2009 SSW event

· TEC enhancement in the South American Sector

15 UT 15 UT

04/12/20239 SA21C, Fall AG 2013

TEC Response

· Typical day-to-day variability in TEC · TEC change during the 2009 SSW event

· TEC suppression in the South American Sector

21 UT 21 UT

04/12/202310 SA21C, Fall AG 2013

· IDA4D results confirms the observed ionopsheric changes reported by Goncharenko et al. [2010].

· 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.

· In this study we extend previous studies and examine the global response of the ionosphere to SSWs using the IDA4D assimilative model.

04/12/202311 SA21C, Fall AG 2013

Avg. Day to Day TEC Variability

UT = 00 UT = 03 UT = 06 UT = 09

UT = 12 UT = 15 UT = 18 UT = 21

DTEC12

First EOF: TEC Response on Jan. 26

UT = 00 UT = 03 UT = 06 UT = 09

UT = 12 UT = 15 UT = 18 UT = 21

DTEC13

First EOF:TEC Response on Jan. 27

UT = 00 UT = 03 UT = 06 UT = 09

UT = 12 UT = 15 UT = 18 UT = 21

DTEC14

First EOF:TEC Response on Jan. 28

UT = 00 UT = 03 UT = 06 UT = 09

UT = 12 UT = 15 UT = 18 UT = 21

DTEC15

First EOF: TEC Response on Feb. 1

UT = 00 UT = 03 UT = 06 UT = 09

UT = 12 UT = 15 UT = 18 UT = 21

DTEC16

· Increased upward drifts due to dynamo electric field· Plasma is lifted to higher altitudes· Slower recombination · Increase in plasma density· EIA fed by this plasma

NE Response

Goncharenko et al. 2010 GRL

Fejer et al. 2010 JGR

17

NE Response

04/12/202318 electrons/m3

· American Sector· Jan 22, Jan 27, and Feb 7, 2009

PRE SSW

SSW

POST SSW

Neincrease

NE Response

04/12/202319electrons/m3

· Asia Pacific Sector· Jan 22, Jan 27, and Feb 7, 2009

PRE SSW

SSW

POST SSW

Nedecrease

· 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: 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.

Conclusions

04/12/202320 SA21C, Fall AG 2013