John Bosco Habarulema and Many Contributors South …...Department of Physics and Electronics, Rhodes University, Grahamstown 6140, South Africa 08 September 2016 John Bosco Habarulema,

New/Recent results about POSSIBLE contribution of low latitudeelectrodynamics to mid-latitude electron density changes

John Bosco Habarulema and Many ContributorsSouth African National Space Agency (SANSA), Hermanus, South AfricaDepartment of Physics and Electronics, Rhodes University, Grahamstown

6140, South Africa

08 September 2016

John Bosco Habarulema, Seminar at ISR, Boston College Low latitude contribution to mid-latitude ionospheric changes

Introduction

How and when?Under what conditions do low latitude changes cause significantvariability in mid-latitude ionospheric dynamics?

Most obvious answer would be ...During storm conditions and through the expansion of equatorialionisation anomaly towards mid-latitudes

Requires..Modification of low latitude electrodynamicsEnhancement of eastward electric fields

This is too simplistic and results discussed in this talk show thatwe do not FULLY understand all the details of what is happeningin low/equatorial latitudes


Role of transequatorial winds

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Similar storm-time study is complicated as the ionosphere and thermosphereare under the influence of both internal and external dynamical andelectrodynamical sources e.g. magnetospheric and disturbance dynamo electricfield contributions as well as global changes in thermospheric neutral wind


Storm-time large scale TIDs

Mostly equatorward from either hemisphereFrequently observed with primary source being the auroral/high latitude regionsin both hemispheres

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Equatorward TIDs have been extensively reported using different data sources.John Bosco Habarulema, Seminar at ISR, Boston College Low latitude contribution to mid-latitude ionospheric changes

Storm-time wave structures of equatorial origin?

Different observationsPart of this talk will show recent results about possible waveactivity in low/equatorial latitudes. Generated waves seem topropagate in poleward directions (in both hemispheres)


Gravity wave generation during storm conditionsDuring storms, significant amount of energy is deposited intoauroral regions

Auroral regionsGravity waves are generated through

Direct heating of the atmosphere (Joule/particle-particleheating)Force J× Bo which is transfered from the ionized componentto the neutrals through collisions (Lorentz coupling).Geomagnetic field is almost vertical and Lorentz coupling justtransfers momentum horizontally to the neutral gas

Equatorial regionsJoule coupling: Direct heating of the atmosphere(Joule/particle-particle heating).Lorentz force J× Bo at the geomagnetic equator is vertical


Case study: 09 March 2012

400

500

600

700

800

900V

sw (

km/s

)(a) Solar wind velocity, Vsw (km/s) and IMF Bz (nT) for 08−10 March 2012

Vsw (km/s)

IMF Bz (nT)

storm main phase onsetshock

08 March 2012 09 March 2012 10 March 201200 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00

−20

−10

0

10

20

30

IMF

Bz

(nT

)

00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21−20

−15

−10

−5

0

5

10

15

IEF

(m

V/m

)

(b) Interplanetary electric field, IEF (mV/m) and SYM−H (nT)

IEF (mV/m)

SYM−H (nT)

08 March 2012 09 March 2012 10 March 2012Time (UT)

−150

−120

−90

−60

−30

0

30

60

SY

M−

H (

nT)


On a global scale

Study based on GNSS TEC data derivedfrom over 2700 GNSS receiver stations,at 30 second temporal resolution,

dt ∝ TECf 2 TEC =∫ s

soNeds (1)

Ne is the electron concentration, dt is the time delayexperienced by the signal, TEC is the total electron contentand f is the frequency of propagationat ionospheric pierce points RATHER than over receiverstations,and considering elevation threshold of 20 degrees


Back ground and ∆TEC changes{

vT f (t)i ,j = at4i ,j + bt3i ,j + ct2i ,j + dti ,j + ε, for j = 1, 2, ..., 31∆TEC(t)i ,j = TEC(t)i ,j − vT f (t)i ,j , ∀i , j

where i = 1, 2, ..., 2500+ is the number of considered receiver stations, j = 1, 2, ..., 31 is the number ofsatellites, vT f (t) and TEC(t) represent fitted and actual vertical TEC at time t; and the coefficients a, b, c, d areobtained through the least-squares method, ε is the residual error of the fitting process.

14 16 18 20 220

10

20

30

40

TE

C (

TE

CU

)

ADIS (9.04°S, 38.77°E)

PRN 3Ethiopia

VTEC

Fitted VTEC

14 15 16 17 18 19 20 21 22−5−4−3−2−1

012345

Time (UT)

∆ T

EC

(T

EC

U)

14 16 18 20 220

10

20

30

40

TE

C (

TE

CU

)

TDOU (23.08°S, 30.38°E)

PRN 4South Africa

14 16 18 20 22−2

−1

0

1

2

Time (UT)

∆ T

EC

(T

EC

U)

Geographic longitude (degrees)

Geo

grap

hic

latit

ude

(deg

rees

)

09 March 2012: 0710 UT

−180

−150

−120 −9

0−6

0−3

0 0 30 60 90 120

150

180

−90

−75

−60

−45

−30

−15

0

15

30

45

60

75

90

∆ T

EC

(T

EC

U)

−5

−4

−3

−2

−1

0

1

2

3

4

5


∆TEC animation: 10 min, 0600-1200 UT


Different sectors

Time (UT)

Geo

grap

hic

latit

ude

(a). American sector: 60°S − 30°N LAT and 40°W − 70°W LON

2 4 6 8 10 12 14 16 18 20 22 24−60

−50

−40

−30

−20

−10

0

10

20

30

∆ T

EC

(T

EC

U)

−5

−4

−3

−2

−1

0

1

2

3

4

5

Time (UT)

Geo

grap

hic

latit

ude

(b). African sector: 40°S − 45°N LAT and 10° − 40°E LON

2 4 6 8 10 12 14 16 18 20 22 24−40

−30

−20

−10

0

10

20

30

40

∆ T

EC

(T

EC

U)

−5

−4

−3

−2

−1

0

1

2

3

4

5

Time (UT)

Geo

grap

hic

latit

ude

(c). Asian sector: 15°S − 30°N LAT and 80°E − 110°E LON

2 4 6 8 10 12 14 16 18 20 22 24−15

−10

−5

0

5

10

15

20

25

30

∆ T

EC

(T

EC

U)

−5

−4

−3

−2

−1

0

1

2

3

4

5

−5

−2.5

0

2.5

5American sector 5°N 10°S 20°S

(d). ∆TEC (TECU) for selected latitudes

−5

−2.5

0

2.5

5African sector 13°N 5°N 5°S

∆ T

EC

(T

EC

U)

0 2 4 6 8 10 12 14 16 18 20 22 24−5

−2.5

0

2.5

5Asian sector 15°N 5°N 5°S

Time (UT)


Such waves can reach midlatitudes (South Africa)

0

0.5

1

1.5

2

2.5 a

∼ 26o longitude, South African data

RT

EC

GRHM, 33.3o S

ANTH, 30.7o S

MFKG, 25.8o S

00 06 12 18 00 06 12 18 00 06 12 18 00

0.6

0.8

1

1.2

1.4

1.6

Rfo

F2

bGrahamstown (GR13L) ionosonde data

08 March 2012 09 March 2012 10 March 2012Time (UT)

Shows approximate shift in peak occurrence in the poleward direction

Positive storm phase over MFKG and ANTH. Time shift in peakoccurrence (10:15 UT and 10:18 UT for MFKG and ANTHrespectively). Similar peak over GRHM at 10:24 UT? Computedvelocity for MFKG-ANTH path is about 500 m/s.


NmF2 changes from ionosonde

00 06 12 18 00 06 12 18 00 06 12 18 00200

250

300

350

400hm

F2

(km

)

GR13L

08 March 2012 09 March 2012 10 March 2012

log1

0 N

mF

2 (c

m−3)

11

11.5

12

00 06 12 18 00 06 12 18 00 06 12 18 00200

250

300

350

400

hmF

2 (k

m)

MU12K

08 March 2012 09 March 2012 10 March 2012

Time (UT, hr)

log1

0 N

mF

2 (c

m−3)

11

11.5

12

Both storm effects seen in the “same mid-latitude” region. See GR13L(33.3◦S) and MU12K (24.4◦S)


What is the possible driver of poleward waves?

Solar quiet wind dynamo current system (combination of neutralwinds, diurnal and semi-diurnal atmospheric tides); sq is caused bywinds as a result of differential heating of the atmosphereLeads to the eastward electrostatic electric field from dawn to dusksectorsEast ward electric field perpendicular to B creates current (Hallcurrent or cowling conductivity).Hall current is carried by upward moving electrons causingpolarisation electric field (perpendicular to B).

Low latitude electrodynamicsThis E⊥B is the one responsible for generating the eastwardelectrojet (EEJ) which flows within ±2◦ from the geomagneticequator.The EEJ causes strong enhancements in magnetometerobservations (H) within ±5◦ from the geomagnetic equator.


Vertical drifts measurements

Differential magnetometer approachUsed magnetometer data in sectors without direct E× Binformation

A station away from the equator ±6◦ − 9◦ will have anear-zero EEJ response, but have an identical response to ringand sq currents as the equatorial station.Direct subtraction of H therefore gives the EEJ contribution.Day-time EEJ∝ E× B

EEJ summary∆H ⇔ East ward electrostatic E ⇔ Polarised E ⇔ EEJ ⇔ E× B

For a charged particle, mdVdt = q(E + V× B)︸︷︷︸Lorentz Force

+ Fnon EM︸︷︷︸Gravity

;

For E⊥B, V = E×BB2 (drift velocity)John Bosco Habarulema, Seminar at ISR, Boston College Low latitude contribution to mid-latitude ionospheric changes

Link between ∆H and Ne, solar activity

∆H ∝ EEJ ∝ E× B

EEJ is related to ionospheric conductivity

EEJ ∝ σE

In the E-region, conductivity is directly related to peak electrondensity of the day-time

σ ∝ NmE

NmE is directly related to the ionising radiation

σ ∝ F 10.7/SSN

Direct relationship between ∆H and NmE showed that NmEincrease of 10% directly led to 10% increase in ∆H (Richmond,1973: Equatorial electrojet: I. Development of a model includingwinds and instabilities, JASTP)


Physical mechanisms

00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 00−60

−40

−20

0

20

40

60

80

100

120

140

160

∆H (

nT)

(a) American sector: JIC, LT=UT−5

09 March 2012

25 March 2012

00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 00−60

−40

−20

0

20

40

60

80

100

120

140

160

∆H (

nT)

(b) African sector: AAE, LT=UT+3

09 March 2012

25 March 2012

00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 00−60

−40

−20

0

20

40

60

80

100

120

140

160

Time (UT)

∆H (

nT)

(c) Indian sector: TIR, LT=UT+5.5

09 March 2012

25 March 2012

Time (UT)

Geo

grap

hic

latit

ude


2 4 6 8 10 12 14 16 18 20 22 24−60

−50

−40

−30

−20

−10

0

10

20

30

∆ T

EC

(T

EC

U)

−5

−4

−3

−2

−1

0

1

2

3

4

5

0

5

10

15

20

25

30

JU

LIA

E×B

(m

/s)

Time (UT)

Peaks in JULIA drifts at 1552 UT and 1818 UT

correspond to existance of TID signatures

in TEC over the South American sector

(b). JULIA E×B (m/s) and ∆H (nT) over JIC

00 02 04 06 08 10 12 14 16 18 20 22 00−80

−40

0

40

80

120

160

JIC

∆H

(nT

)


Low Latitude Physics

Increase in E× B lifts ionospheric plasma to higher altitudes(stays there longer because recombination rate is slower)Pressure gradients and gravitational forces move plasma alongthe geomagnetic field lines on both sides of the equator

Vd =1

neq∇P× B

B2 Electron diamagnetic drift velocity

Vg =me

g × BB2 Gravitational drift velocity

ClaimTID related waves (density/pressure imbalance) move with plasmaalong the geomagnetic field lines. Since E× B is responsible forthe formation of the EIA, then it could also act as a modulator ofthe generated TIDs

Details in Habarulema, J. B., Z. T. Katamzi, E. Yizengaw, Y. Yamazaki, and G. Seemala (2016), Simultaneous

storm time equatorward and poleward large-scale TIDs on a global scale, Geophys. Res. Lett., 43, 6678-6686


Suggested and numerically shown by Chimonas, (1969)


What next? Use RO data for vertical studies

Alti

tude

(km

)

(a)

Ne over MU12K (22.4°S, 30.9°E) for 10/03/2012

0 3 6 9 12 15 18 21 24100

200

300

400

500

600

700

Ne

(cm

−3 )

5

10

15

x 105

0 3 6 9 12 15 18 21 240

5

10

15

20

25

Ne,

cm

−3

(× 1

05) (b) Ionosonde N

e at 250 km, 300 km, 350 km

00 03 06 09 12 15 18 21 000

5

10

15

20

25

Ne,

cm

−3

(× 1

05) (c) COSMIC Ne at 250 km, 300 km, 350 km

9 9.5 10 10.5 11 11.5 1212

13

14

15

16

17

Ne,

cm

−3

(× 1

05)

Time (UT)

(d) MU12K Ne at 250 km, 300 km, 350 km

Alti

tude

(km

)

(e)

Ne over LV12P (28.5°S, 21.2°E) for 01/10/2012

0 3 6 9 12 15 18 21 24100

200

300

400

500

600

700

Ne

(cm

−3 )

5

10

15

x 105

0 3 6 9 12 15 18 21 240

5

10

15

20

25

Ne,

cm

−3

(× 1

05) (f) Ionosonde N

e at 250 km, 300 km, 350 km

00 03 06 09 12 15 18 21 000

5

10

15

20

25

Ne,

cm

−3

(× 1

05) (g) COSMIC N

e at 250 km, 300 km, 350 km

4.5 5 5.5 6 6.5 72

4

6

8

Time (UT)

Ne,

cm

−3

(× 1

05)

(h) LV12P Ne at 250 km, 300 km, 350 km


How reliable is RO data? Midlatitude results

2003 2004 2005 2007 2008 2009 2011 2012 2014 2015 2016100

150

200

250

300

350

400

450

Time (Years)

hmF

2 (k

m)

a

CHAMP Ionosonde COSMIC

180 200 220 240 260 280 300 320 340 360 380 400100

150

200

250

300

350

400

450

Ionosonde hmF2 (km)

CH

AM

P/C

OS

MIC

hm

F2

(km

)

No=217, r=0.7652

hmF2RO

=0.731hmF2iono

+84.69

b

2003 2004 2005 2007 2008 2009 2011 2012 2014 2015 20160

0.5

1

1.5

2x 10

12

Time (Years)

Nm

F2

(m−

3 )

c CHAMPIonosondeCOSMIC

0 0.5 1 1.5 2

x 1012

0

0.5

1

1.5

2x 10

12

CH

AM

P/C

OS

MIC

Nm

F2

(m−

3 )

Ionosonde NmF2 (m−3)

dN

o=217, r=0.9646

NmF2RO

=1.064NmF2iono

−5×109

Storm-time long term comparison over Grahamstown, GR13L(33.3◦S). An important requirement is to manually check and scaleionograms where necessary. Habarulema and Carelse, GRL (2016)


Errors associated with RO NmF2 and hmF2 data

2003 2005 2008 2011 2014 2016−90

−60

−30

0

30

60

90

∆ hm

F2

(km

)a

−90 −60 −30 0 30 60 900

10

20

30

Fre

quen

cy (

%)

∆ hmF2 (km)

cmean=9.77 km

σ=24.82 km

2003 2005 2008 2011 2014 2016−4

−2

0

2

4

6

8x 10

11

∆ N

mF

2 (m

−3 )

Time (Years)

b

−4 −2 0 2 4 6 8

x 1011

0

10

20

30

40

50

∆ NmF2 (m−3)

Fre

quen

cy (

%)

d mean=3.33×1010 m−3

σ=1.24×1011 m−3

78% of ∆hmF2 is within 30 km and statistically agrees with quiet timeand low solar activity studies (Chu et al., 2010; Krankowski et al., 2011)


How often does this happen? a look at equatorward TIDs

Time (UT)

Latit

ude

(°)

(a) 9 March 2012

0 2 4 6 8 10 12 14 16 18 20 22 24−40−38−36−34−32−30−28−26−24−22−20−18−16−14−12−10

∆TE

C (

TE

CU

)

−3

−2

−1

0

1

2

3

Time (UT)

Latit

ude

(°)

(d) 01 October 2012

0 2 4 6 8 10 12 14 16 18 20 22 24−40−38−36−34−32−30−28−26−24−22−20−18−16−14−12−10

∆TE

C (

TE

CU

)

−3

−2

−1

0

1

2

3

Time (UT)

Latit

ude

(°)

(b) 24 April 2012

0 2 4 6 8 10 12 14 16 18 20 22 24−40−38−36−34−32−30−28−26−24−22−20−18−16−14−12−10

∆TE

C (

TE

CU

)

−3

−2

−1

0

1

2

3

Time (UT)

Latit

ude

(°)

(e) 8 October 2012

0 2 4 6 8 10 12 14 16 18 20 22 24−40−38−36−34−32−30−28−26−24−22−20−18−16−14−12−10

∆TE

C (

TE

CU

)

−3

−2

−1

0

1

2

3

Time (UT)

Latit

ude

(°)

(c) 15 July 2012

0 2 4 6 8 10 12 14 16 18 20 22 24−40−38−36−34−32−30−28−26−24−22−20−18−16−14−12−10

∆TE

C (

TE

CU

)

−3

−2

−1

0

1

2

3

Time (UT)

Latit

ude

(°)

(f) 14 November 2012

0 2 4 6 8 10 12 14 16 18 20 22 24−40−38−36−34−32−30−28−26−24−22−20−18−16−14−12−10

∆TE

C (

TE

CU

)

−3

−2

−1

0

1

2

3

10◦E-40◦E latitude;10◦S-40◦S longitudeEquatorward wavesalways present duringstrong storms.In (b), velocities are611± 37 m/s (5-6UT), 306± 18 m/s(9-10 UT) and244± 15 m/s (10-11UT)For (c), 306± 18 m/s(5-6 UT) and 367± 22m/s (10-11 UT)Period of at least 1hourNEED A STORM-TIMEANALYSIS FOR LOWLATITUDES


Conclusions

Time (UT)

Geo

grap

hic

latit

ude


2 4 6 8 10 12 14 16 18 20 22 24−60

−50

−40

−30

−20

−10

0

10

20

30

∆ T

EC

(T

EC

U)

−5

−4

−3

−2

−1

0

1

2

3

4

5

Time (UT)

Geo

grap

hic

latit

ude

(b). African sector: 40°S − 45°N LAT and 10° − 40°E LON

2 4 6 8 10 12 14 16 18 20 22 24−40

−30

−20

−10

0

10

20

30

40

∆ T

EC

(T

EC

U)

−5

−4

−3

−2

−1

0

1

2

3

4

5

Time (UT)

Geo

grap

hic

latit

ude

(c). Asian sector: 15°S − 30°N LAT and 80°E − 110°E LON

2 4 6 8 10 12 14 16 18 20 22 24−15

−10

−5

0

5

10

15

20

25

30

∆ T

EC

(T

EC

U)

−5

−4

−3

−2

−1

0

1

2

3

4

5

−5

−2.5

0

2.5

5American sector 5°N 10°S 20°S

(d). ∆TEC (TECU) for selected latitudes

−5

−2.5

0

2.5

5African sector 13°N 5°N 5°S

∆ T

EC

(T

EC

U)

0 2 4 6 8 10 12 14 16 18 20 22 24−5

−2.5

0

2.5

5Asian sector 15°N 5°N 5°S

Time (UT)

Low latitude electrodynamics changes contributes to poleward TIDs thatcan reach midlatitudes. It is not yet clear why equatorward propagation ispredominantly in Indian/Asian sector.


End

Thank you


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John Bosco Habarulema and Many Contributors South …...Department of Physics and Electronics, Rhodes University, Grahamstown 6140, South Africa 08 September 2016 John Bosco Habarulema,