Ionospheric Scintillation in

Africa: A SCINDA Perspective

AMISR Meeting

Boston College

01 March 2012

Keith Groves1 Ron Caton2

Charles Carrano1 Chris Bridgwood1

Joshua Orfield2

1Boston College 2Air Force Research Lab

• Motivation: Scintillation Effects

• SCIntillation Network Decision Aid (SCINDA)

• International Space Weather Initiative (ISWI)

• Some Results

• Current and Future Efforts

OUTLINE

PRN 7

2

What is Scintillation?

• Regional UHF SATCOM outages for extended periods (hours)

• Increased GNSS position/navigation/timing errors

• Degraded High Frequency (HF) radio communication 3

SCINTILLATION =

Rapid amplitude

and phase

fluctuations of

radio signals in

space due to

turbulence

AFRL Best Climatology Model had a

Gap in the Atlantic

• Gap in scintillation activity

predicted by climatological

model near equinoxes in the

Atlantic sector

• The gap existed because of an

artifact in the model and an

absence of information (data) to

improve it

• Raised the question: What about

the validity of results over Africa?

• Model remains unvalidated, but

data collection from solar min to

solar max will enable

improvement

Scintillation Activity in Africa

• Scintillation activity across Africa

assumed high based on satellite

observations, but ground-based

measurements are needed

• C/NOFS sees similar maximum in

activity over Africa

• Worked with IHY (2005-09) & ISWI

(2009-present) to identify host nation

partners & collaborators

• Goal is to establish robust

monitoring network with scientific

collaboration across Africa, Asia and

South America

Strength of scintillations over Africa

unknown

Adapted from S.Y. Su, 2005

Present and anticipated thru 2013

SCINDA Ground Stations

30N

0

30S

210E 240E 270E 300E 330E 0 30E 60E 90E 120E 150E

Existing Sites Future UN ISWI Sites Other collaboration

LISN Domain Recent

SCINDA Focus

VHF & GPS Sensor Data Nairobi, Kenya, 01 Oct 2011

SCINDA Science

• Exploit data for more scientific studies on both local and global scintillation phenomena

– Identify and explain differences (and similarities) between activity and irregularities in Africa relative to other longitude sectors

– Storm-time behavior; SEDS/SAPS in African sector; African landmass spans low- to north and south mid-latitudes

– Terrestrial coupling; 4-cell pattern in TEC/scintillation, local gradients, anomaly characteristics

– Ultimate goal is to forecast equatorial Spread F

Longitudinal Variations: Continental Scale

Synoptic scale features can be resolved with current network, but better resolution is needed

ASI

KIN

ZNZ ZNZ ZNZ ZNZ

ASI ASI ASI

KIN KIN KIN

EA

ST

W

ES

T

CE

NT

RA

L

14 Oct 15 Oct 16 Oct 27 Oct

DMSP Bubbles 1989 - 2002 D

ay o

f Y

ear

Longitude

365

273

182

91

1

Africa India Pacific America Atlantic

0 30 60 90 120 150 180 210 240 270 300 330 360

45-50

40-45

35-40

30-35

25-30

20-25

15-20

10-15

5-10

0-5

EPB Occurrence

Rate

Magnetic field aligned

with terminator

From Burke & Huang, 2004

Equatorial Bubbles in Africa

• Bubble envelop frequently shows

very large longitudinal extent relative

to other longitude sectors

• Occurrence frequency peaks over

Africa as well

• Equatorial coherent backscatter

radar can address this issue

Satellite observations exhibit

unique characteristics

Determining Bubble Altitude

• For scintillation activity to reach Ascension Island, bubbles must rise to more than 1000 km altitude, spreading to over 3000 km N-S extent

• During solar minimum, almost no bubbles reach these altitudes; N-S extent typically ~ 2000 km

12

SOLAR MIN NOW

Relative Occurrence of Bubbles Exceeding 1000 km Altitude

• Sites at different latitudes see different levels of activity depending on bubble altitude

• Bubbles need to extend above 1000 km to reach ASI; only ~400 km to reach Cape Verde

• Data will improve model for predicting bubble extent and understanding electrodynamics 13

Longitudinal Climatology 2011

14

• Africa shows elements of the climatology from both the Pacific and the American sectors

• Unusual distribution of late activity (~midnight) development needs explanation; not observed elsewhere

Frequency Dependence of Scintillation Climatology

• Differences in seasonal and diurnal occurrence statistics of VHF & GPS scintillation in western South America

• GPS L1 signals not sensitive for detecting irregularities in low density plasmas (< 106 e/cc, ~< 50 TEC)

L-band peaks here

VHF peaks here

Requires local

ground-based

observations

to detect

16

• Climatology across central-west Africa different from anywhere else

• Not all features explained by magnetic terminator alignment

• Terrestrial coupling may play a role

Continent-scale Climatology

Magnetic Storm Effects (Modest) 22-24 Jan

Magnetic Equator

Magnetic Storm Effects (22-24 Jan)

Mid-latitude Response

2011-2013 Plans (unofficial)

• Install an additional 4-5 sites in Africa, 2-3 other locations in S.E. Asia/Pacific

– Higher sensor density needed for detailed studies, e.g. LISN

• Improve infrastructure/capability at functional sites in Africa

– Solar panels, robust power systems, mobile data transfer

– Add VHF scintillation/drift sensors and possibly optical imagers

• Develop improved multi-frequency LEO beacon receiver systems focused on next-generation beacon design (still TBD); up to six equatorial satellites in constellation (2015)

– New sensors useful throughout SCINDA & LISN networks

• Install a coherent backscatter VHF radar near magnetic equator (talk tomorrow at 09:30 a.m.!)

Campaign Summary 25 APRIL 2009 – Day 115

Perp-B Scan

Off Perp-B

Scans

Summary

• Preliminary review of results from Africa confirm satellite climatology, but temporal dependence for June/July period are surprising

• Infrastructure remains an issue but improvements are tractable

– Critical for both long-term and case studies

• VHF coherent backscatter radar combined with satellite observations (C/NOFS) near peak of solar cycle should provide more insight on the nature of bubbles over Africa

• Incoherent scatter radar will provide unique knowledge of the regional structure of the African ionosphere as well as the physics of the associated electrodynamics

Proposed Site Photo

Thanks for your attention.

Dr. Keith Groves

617-552-6313

Keith.Groves@bc.edu