Ionospheric Scintillation in
Africa: A SCINDA Perspective
Keith Groves1
Ron Caton2
Charles Carrano1
Chris Bridgwood1
Joshua Orfield2
AMISR Meeting
1Boston
College
2Air Force Research Lab
Boston College
01 March 2012
OUTLINE
• Motivation: Scintillation Effects
• SCIntillation Network Decision Aid (SCINDA)
• International Space Weather Initiative (ISWI)
• Some Results
• Current and Future Efforts
PRN 7
2
What is Scintillation?
SCINTILLATION =
Rapid amplitude
and phase
fluctuations of
radio signals in
space due to
turbulence
• Regional UHF SATCOM outages for extended periods (hours)
• Increased GNSS position/navigation/timing errors
• Degraded High Frequency (HF) radio communication
3
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
Strength of scintillations over Africa
unknown
• 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
Adapted from S.Y. Su, 2005
SCINDA Ground Stations
Present and anticipated thru 2013
30N
0
30S
Recent
SCINDA Focus
LISN Domain
210E
240E
270E
Existing Sites
300E
330E
0
30E
Future UN ISWI Sites
60E
90E
120E
Other collaboration
150E
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
EAST
CENTRAL
WEST
14 Oct
15 Oct
16 Oct
27 Oct
ASI
ASI
ASI
ASI
KIN
KIN
KIN
KIN
ZNZ
ZNZ
ZNZ
ZNZ
Synoptic scale features can be resolved with current network, but
better resolution is needed
DMSP Bubbles 1989 - 2002
Day of Year
365
Africa
India
Pacific
America
Atlantic
EPB
Occurrence
Rate
273
45-50
40-45
35-40
30-35
182
25-30
20-25
15-20
91
10-15
5-10
0-5
1
0
30
60
Magnetic field aligned
with terminator
90
120
150
180
210
240
270
300
330
360
Longitude
From Burke & Huang, 2004
Equatorial Bubbles in Africa
Satellite observations exhibit
unique characteristics
• 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
Determining Bubble Altitude
SOLAR MIN
NOW
• For scintillation activity to reach Ascension Island, bubbles
must
12
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
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
• 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)
VHF peaks here
Requires local
ground-based
observations
to detect
L-band peaks here
Continent-scale Climatology
• Climatology
across centralwest Africa
different from
anywhere else
• Not all features
explained by
magnetic
terminator
alignment
• Terrestrial
coupling may
play a role
16
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