Space Weather of the Ionospheric S4 Scintillation
Tiger J.Y. Liu1, S. P. Chen1, W.H. Yeh2
1Institute of Space Science, National Central University, TaoYuan, Taiwan2National Space Origination, HsinChu, Taiwan
Taiwan Ionospheric Group for Education and Research (TIGER)
Taiwan Ionospheric Group for Earthquake Research (TIGER)
Content
• Introduction
•FORMOSAT-3/COSMIC Ionospheric S4 Scintillation
•Modeling F3/C S4 Scintillation
•Conclusion
GPS Radio Occultation
αWavelength and amplitude of in the vertical direction
Global 3D structure
Daily sounding:
2500-1500 profiles
Total sounding: 4,000,000+ profiles
Ionospheric F3/C RO Sounding
Ionospheric Scintillation
Basu et al. [JASTP 2002]
2400LT1800LT
1200LT
FORMOSAT-3/COSMIC S4-index measures signal-to-noise intensity fluctuations from the raw 50-Hz L1 amplitude measurements and these intensity measurements and recorded in a 1-Hz data stream.
: mean RMS intensity within 1 sec (mean value of 50 data)
: a low-pass filtered 1 sec mean RMS intensity(Low-pass filtered , to be short.)
COSMIC calculated S4-index
Density irregularity
𝑆𝑐𝑖𝑛𝑡𝑖𝑙𝑙𝑎𝑡𝑖𝑜𝑛 ∝∆𝑁
𝑁
S4Max
S4Max
Solar minimum of 2008 Liu et al. [SGP 2015]
Solar maximum of 2013 Liu et al. [SGP 2015]
The F-region (i.e. 150-450km) S4max in 2007-2014.
Liu et al. [SGP 2015]
The E-region (i.e. 80-130km) S4max in 2007-2014.
Liu et al. [SGP 2015]
The conversion of the space based F3/C
RO scintillation to the ground-based one.
Liu et al. [SGP 2015]
A Gnomonic projection of annual mean
diurnal S4max variation
The global S4-index diurnal variation in Gnomonic projection during
(a) solar minimum year 2008, and (b) solar maximum year 2013.
The geographic distribution of S4max in solar minimum
Liu et al. [SGP 2015]
The geographic distribution of S4max in solar maximum
Liu et al. [SGP 2015]
Observation (2007-2014)
An Empirical Model of the Converted S4 index
• S4 = SDiurnal×SSeasonal×SDip×SF10.7
• Low Latitude and High Latitude
•Diurnal Variation
• Seasonal Variation
• Latitudinal Variation
• Solar activity Variation
•High Latitude
The weighting that combines the low latitude model weight (red
line), and the high latitude model weight (blue line) of the model.
Dash lines depicts the boundary of the low latitudinal part of
±45°dip, the high latitudinal part of±65°dip, and the intersection
points at±55°dip with 50% weighting for each parts.
Low Latitude and High Latitude
The diurnal variation of the F3/C S4-index at dip-equator during
2007-2014 (blue curve) and the model fitting (red curve). The
errorbar denotes±1 standard deviation.
Diurnal Variation
The RMSE between the F3/C S4-index monthly variation at dip-equator during
2007-2014 and the nth-order polynomial retrieval. Note that the RMSE
becomes stable after the 6th-order polynomial retrieval (red circle).
Seasonal Variation: Polynomial Fit
The monthly variation of the F3/C S4-index at dip-equator at selected
longitudinal sectors during 2007-2014 (blue curves) and corresponding 6th-order
polynomial retrievals (red curves). The errorbar denotes±1 standard deviation.
Seasonal Variation
The total mean of F3/C S4-index during 2007-2014, note that the red
solid/dot-line curve indicates the dip-latitudes of the Northern/Southern
High-Latitude S4 peaks along longitudinal direction, the black solid/dash
line is the Northern Low-Latitude peaks and its mirror projection to the
dip-equator as the Southern Low-Latitude peaks.
Latitudinal Variation – 4 Peaks
The F3/C S4-index dip-latitudinal variation (blue curve) and the model simulation
(red curve), which is the summation of the Equatorial part (gray curve), the Low-
latitudinal part (green curve), and the High-latitudinal part (black curve).
Latitudinal Variation
The dip-latitudes of the four major peaks under increasing PF107. The
blue lines indicate F3/C observation, and the red lines are model fitting.
Latitudinal Variation – Solar Activity
The dip-latitudinal distribution of the F3/C S4-index at selected longitudes
during 2007-2014 (blue curves), and the model fitting (red curves).
Latitudinal Variation
The F3/C S4-index collocates with increasing PF107 during 2007-
2014 (blue curve), and the model fitting (red line).
Solar Activity Variation
The (a) diurnal variation (b) longitudinal variation (c) seasonal variation (d) solar
activity variation of F3/C S4-index in high latitude region (60°-85°dip) of
northern/southern hemisphere (left/right panel) during 2007-2014 (blue curve),
and corresponding model fitting (red line).
High Latitude Part
Diurnal Variation
Longitudinal Variation
Seasonal Variation
Solar Activity Variation
Observation Model Output
Observation
Model Output
(a) The locations of 3 Space Weather Services (SWS) ground based scintillation observation
sites, which are DARWIN, WEIPA, and NIUE. The red cross at (-14°N, 155°E) is the median
location of the three low latitude sites. (b) The total median S4-index of the SWS network
(blue lines) comparing with F3/C S4-index (black lines) and the model simulated S4-index
(red lines) during the solar minimum, moderate and maximum periods.
(a) The locations of the 9
SCINDA ground based
scintillation observation sites.
(b) The S4-index of the
SCINDA network (blue lines)
comparing with F3/C S4-index
(black lines) and the model
simulated S4-index (red lines)
in 2013. The errorbar denotes
±1 standard deviation.
Conclusion (I)
• The most prominent signatures of the F3/C S4 max in the E- (F-)region are in middle (equatorial- and low-) latitudes of the Summer J-month (equinox) months.
• The F3/C S4 max in the E-region is mainly contributed by the Es (sporadic-E) layer. Neutral wind is essential!
• The F3/C S4 max in the F-region lies between 20°N and 20°S and expends to higher latitudes in the equinox and D months. E×B plasma fountain is essential!
Conclusion (II)
• The worst case scintillation on the ground appears in the low-latitude of ±30°peaking around ±20°mLat from the post-sunset of 1900 MLT till post-midnight of 0200-0300 MLT.
• The place experienced the worst-case scintillation is the low-latitude ionosphere between South America and Africa.
• An empirical F3/C S4 model (GNSS-S4) has been developed, which needs to be validated and calibrated by ground-based GPS S4 scintillation observations.
Thank you!!!
34
Thank you
