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GPS Scintillation effects as observed from a location beyond the anomaly crest in the Indian longitude sector Sarbani Ray Institute of Radio Physics and Electronics University of Calcutta Calcutta, India Ankita Pal Babita Chandel Applied Science

SLIDE 1

GPS Scintillation effects as observed from a location beyond the anomaly crest in the Indian longitude sector

Sarbani Ray Institute of Radio Physics and Electronics University of Calcutta Calcutta, India Ankita Pal Babita Chandel Applied Science and Physics Department Sri Sai University Palampur, India

SLIDE 2

Introduction

It is well-established that intense low-latitude

scintillations, particularly that observed from locations near the crests of the Equatorial Ionization Anomaly (EIA) have largely impaired the performance of GNSS.

In this paper we present cases of intense

scintillations observed from stations located poleward of the northern crest of the anomaly in the Indian longitude sector and examine the propagation conditions responsible.

SLIDE 3

SHIMLA DELHI JODHPUR CALCUTTA BAGDOGRA LUCKNOW GUWAHATI AIZWAL BHOPAL RAIPUR AHMEDABAD VISHAKHAPATNAM MUMBAI HYDERABAD BANGALORE AGATTI PORT BLAIR TRIVANDRUM

Magnetic Equator

70 75 80 85 90 95 100 105 65 35 30 25 20 10 5

Location of GPS Receivers in India

Northern crest of EIA

Geographic Longitude( deg. E)

Geographic Latitude( deg. N)

PALAMPUR

SLIDE 4

Station Geographic Latitude(deg. N) Geographic Longitude(deg. E) Magnetic Latitude(deg. N) Trivandrum 8.47 76.91 3.66 Bangalore 12.95 77.68 8.22 Hyderabad 17.44 78.47 12.84 Bhopal 23.28 77.34 19.20 Delhi 28.58 77.21 24.93 Shimla 31.09 77.07 27.65 Agatti 10.83 72.18 7.08 Mumbai 19.09 72.85 15.49 Ahmedabad 23.06 72.61 19.68 Jodhpur 26.26 73.05 23.00 Aizwal 23.83 92.62 18.32 Guwahati 26.12 91.59 20.94 Port Blair 11.67 92.72 4.94 Calcutta 22.58 88.38 17.23 Bagdogra 26.68 88.32 21.76 Visakhapatnam 17.72 83.22 12.44 Raipur 21.18 81.74 16.40 Lucknow 26.76 80.88 22.56

Station Geographic and Magnetic coordinates

SLIDE 5

1430-1530UT 1530-1630UT LT=UT+6hr

Scintillation Index

Sv23 Sv30 Sv40 Sv5 Sv39 Sv6 Sv10 Sv24 Sv17 Sv26 30 60 60 30 W E S N

1330-1430UT

Sv39 Sv17 Sv15 Sv40 Sv23 Sv6 Sv30 Sv5 Sv9 Sv42 Sv24 Sv26 Sv10 60 30 60 30 W E S N 30 60 60 30 Sv23 Sv29 Sv30 Sv14 Sv6 Sv42 Sv9 Sv26 Sv10 Sv17 Sv21 Sv40 Sv15 Sv39 W E S N Sv9 Sv17 Sv15 Sv23 Sv21 Sv3 Sv33 Sv56Sv40 Sv39 Sv26 Sv42 Sv6 Sv14 Sv29 60 30 60 30 W E S N

0-5dB 6-10dB 11-15dB 16-20dB >20dB FSC INMARSAT

Elevation-Azimuth plots of GPS satellite tracks observed from Calcutta by GG24 during 1330-1730UT(1930-2330LT) on February 12, 2001. 1630-1730UT Receiver: GG24 Station: Calcutta Date: February 12, 2001

SLIDE 6

LT=UT+6hr

Sv40 Sv33 Sv30 Sv29 Sv25 Sv23 Sv21 Sv15 Sv14 Sv11 Sv9 Sv3 60 30 60 30 W E S N Sv56 Sv42 Sv40 Sv39 Sv33 Sv30 Sv29 Sv25 Sv23 Sv21 Sv17 Sv15 Sv14 Sv9 Sv5 Sv3 60 30 60 30 E W S N Sv56 Sv42 Sv40 Sv39 Sv33 Sv30 Sv29 Sv26 Sv25 Sv23 Sv21 Sv17 Sv15 Sv14 Sv9 Sv5 Sv3 Sv6 60 30 60 30 E W S N Sv40 Sv33 Sv30 Sv29 Sv25 Sv23 Sv22 Sv21 Sv15 Sv14 Sv11 Sv5 60 30 60 30 W E S N

0-5dB 6-10dB 11-15dB 16-20dB >20dB FSC INMARSAT

Scintillation Index

Elevation-Azimuth plots of GPS satellite tracks observed from Calcutta by GG24 during 1730-2130UT(2330-2730LT) on February 12, 2001. 2030-2130 UT 1830-1930 UT 1730 - 1830 UT 1930-2030 UT Receiver: GG24 Station: Calcutta Date: February 12, 2001

SLIDE 7

(Not to scale)

Magnetic N Pole Magnetic S Pole Geomagnetic Field Line Satellite Satellite Magnetic Equator Plasma Bubble Station

S E B F A C D

Geomagnetic Field Line Plasma Bubble Magnetic S Pole Magnetic N Pole Magnetic Equator Satellite

D B2 B1 A C S1 S2

Propagation Geometry

a) b)

SLIDE 8

Calcutta Calcutta Calcutta

Calcutta during

SLIDE 9

y = -3E-06x6 + 0.000x5 - 0.010x4 + 0.192x3 - 1.810x2 + 9.299x - 21.30

5 10 15 20 25 5 10 15 20 25 30

(b) Magnetic Latitude of the center of the maximum propagation angle region vs. Magnetic Latitude of the station

y = 1E-05x5 - 0.001x4 + 0.032x3 - 0.427x2 + 4.430x + 134.2 140 145 150 155 160 165 170 175 180 5 10 15 20 25 30

(a) Maximum propagation angle for the station vs. station Magnetic Latitude

y = -4E-06x6 + 0.000x5 - 0.021x4 + 0.525x3 - 6.812x2 + 46.28x - 127.4 5 10 15 20 25 30 5 10 15 20 25 30 35

Station Magnetic Latitude(deg.N) Maximum Propagation angle(deg.) Station Magnetic Latitude(deg.N)

y = -2E-06x6 + 0.000x5 - 0.163x4 + 17.95x3 - 1109.x2 + 365x - 49944 70 75 80 85 90 95 100 70 75 80 85 90 95 100

(d) Geographic Longitude of the center of the maximum propagation angle region vs. Geographic Longitude of the station

Magnetic latitude(deg.N) Station Geographic Latitude(deg.N) Geographic Latitude(deg.N) Station Geographic Longitude(deg.E) Geographic Longitude(deg.E)

SLIDE 10

FROM PROPAGATION GEOMETRY…

The zone of maximum propagation angle for any

station in the northern magnetic hemisphere is located to the south of the station.

The value of maximum propagation angle for a

particular station depends on the magnetic latitude of the station, progressively increasing as one moves north from the magnetic equator. This is due to the fact that the magnetic field lines have minimum curvature over the magnetic equator, but the field lines gradually converge at higher latitudes and ultimately coalesce at the poles.

SLIDE 11

Subionospheric Longitude(deg.E) Subionospheric Latitude(deg.N) Station: Trivandrum Period: August-October 2004 13UT-14UT 14UT-15UT 15UT-16UT 16UT-17UT

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

LT = UT + 05.17h

SLIDE 12

17UT-18UT 18UT-19UT 19UT-20UT 20UT-21UT

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

LT = UT + 05.17h Station: Trivandrum Period: August-October 2004 Subionospheric Longitude(deg.E) Subionospheric Latitude(deg.N)

SLIDE 13

Maximum Propagation Angle :146.69o Zone: 0.06o to 2.73oN and 73.38o to 76.56o E (geographic) ;-5.35o to -2.10oN (magnetic )

a)Propagation angle map in terms of Subionospheric Latitude and Longitude for Trivandrum. b)Scintillation observed from Trivandrum during 15:00-16:00UT on September 15, 2004. c) Propagation angle map in terms of Magnetic Latitude and Subionospheric Longitude for Trivandrum.

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6 LT = UT + 05.17h

65 70 75 80 85 90

5 10 15

Propagation angle(deg.) Magnetic Latitude(deg.N) Subionospheric Longitude(deg.E)

45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.0 105.0 110.0 115.0 120.0 125.0 130.0 135.0 140.0 145.0 150.0 155.0 160.0 165.0 170.0 175.0 180.0

IGRF-9 (2000) (a) (b) (c)

Subionospheric Longitude(deg.E) Subionospheric Latitude(deg.N)

65 70 75 80 85 90

5 10 15 20

Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

Station: Trivandrum [ Latitude:8.47oN, Longitude: 76.91o E (geographic) ;Magnetic Latitude:3.66oN]

SLIDE 14

Station: Bangalore Period: August-October 2004 LT = UT + 05.17h Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

13UT-14UT 14UT-15UT 15UT-16UT 16UT-17UT

SLIDE 15

Station: Bangalore Period: August-October 2004 LT = UT + 05.17h Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

17UT-18UT 18UT-19UT 19UT-20UT 20UT-21UT

SLIDE 16

Maximum Propagation Angle :155.46o Zone: 4.48o to 6.25oN and 75.73o to 76.50o E (geographic) ;-0.32o to 1.48oN (magnetic )

a)Propagation angle map in terms of Subionospheric Latitude and Longitude for Bangalore. b) Propagation angle map in terms of Magnetic Latitude and Subionospheric Longitude for Bangalore.

IGRF-9 (2000) IGRF-9 (2000)

65 70 75 80 85 90

5 10 15 20

Propagation angle(deg.) Magnetic Latitude(deg.N) Subionospheric Longitude(deg.E)

45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.0 105.0 110.0 115.0 120.0 125.0 130.0 135.0 140.0 145.0 150.0 155.0 160.0 165.0 170.0 175.0 180.0

(b) (a)

Station: Bangalore [ Latitude:12.95oN, Longitude: 77.68o E (geographic) ;Magnetic Latitude:8.22oN]

65 70 75 80 85 90 5 10 15 20 25

Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

SLIDE 17

Station: Hyderabad Period: August-October 2004 LT = UT + 05.17h Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

13UT-14UT 14UT-15UT 15UT-16UT 16UT-17UT

SLIDE 18

Station: Hyderabad Period: August-October 2004 LT = UT + 05.17h Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

17UT-18UT 18UT-19UT 19UT-20UT 20UT-21UT

SLIDE 19

Maximum Propagation Angle : 164.34o Zone: 8.80o to 12.69oN and 76.47o to 80.61o E (geographic) ; 3.71o to 7.92oN (magnetic )

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

LT = UT + 05.17h

65 70 75 80 85 90 5 10 15 20 25

Propagation angle(deg.) Magnetic Latitude(deg.N) Subionospheric Longitude(deg.E)

45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.0 105.0 110.0 115.0 120.0 125.0 130.0 135.0 140.0 145.0 150.0 155.0 160.0 165.0 170.0 175.0 180.0

Subionospheric Longitude(deg.E) Subionospheric Latitude(deg.N)

(b) (a) (c) IGRF-9 (2000) IGRF-9 (2000)

a)Propagation angle map in terms of Subionospheric Latitude and Longitude for Hyderabad. b)Scintillation observed from Hyderabad during 17:00-18:00UT on September 3, 2004. c) Propagation angle map in terms of Magnetic Latitude and Subionospheric Longitude for Hyderabad.

65 70 75 80 85 90 5 10 15 20 25 30

Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

Station: Hyderabad [ Latitude:17.44oN, Longitude: 78.47o E (geographic) ;Magnetic Latitude:12.84oN]

SLIDE 20

Station: Bhopal Period: August-October 2004 LT = UT + 05.17h Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

13UT-14UT 14UT-15UT 15UT-16UT 16UT-17UT

SLIDE 21

Station: Bhopal Period: August-October 2004 LT = UT + 05.17h Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

17UT-18UT 18UT-19UT 19UT-20UT 20UT-21UT

SLIDE 22

Maximum Propagation Angle :176.21o Zone: 14.84o to 16.98oN and 76.06o to 76.52oE (geographic) ; 10.42 to 12.66oN (magnetic)

a)Propagation angle map in terms of Subionospheric Latitude and Longitude for Bhopal. b)Scintillation observed from Bhopal during 17:00-18:00UT on October 28, 2004. c) Propagation angle map in terms of Magnetic Latitude and Subionospheric Longitude for Bhopal.

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

LT = UT + 05.17h

IGRF-9 (2000) IGRF-9 (2000)

Subionospheric Longitude(deg.E) Subionospheric Latitude(deg.N)

(a) (b) (c)

65 70 75 80 85 90 5 10 15 20 25 30

Propagation angle(deg.) Magnetic Latitude(deg.N) Subionospheric Longitude(deg.E)

45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.0 105.0 110.0 115.0 120.0 125.0 130.0 135.0 140.0 145.0 150.0 155.0 160.0 165.0 170.0 175.0 180.0

Station: Bhopal [ Latitude:23.28oN, Longitude: 77.34o E (geographic) ;Magnetic Latitude:19.20oN]

65 70 75 80 85 90 10 15 20 25 30 35

Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

SLIDE 23

Station: Delhi Period: August-October 2004 Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

13UT-14UT 14UT-15UT 15UT-16UT 16UT-17UT LT = UT + 05.17h

SLIDE 24

Station: Delhi Period: August-October 2004 Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

17UT-18UT 18UT-19UT 19UT-20UT 20UT-21UT LT = UT + 05.17h

SLIDE 25

Maximum Propagation Angle : 179.88o Zone: 21.66o to 24.98oN and 76.46o-78.17oE (geographic) ; 17.46o to 21.11oN (magnetic )

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

LT = UT + 05.17h

(a) (b) (c) IGRF-9 (2000) IGRF-9 (2000)

Subionospheric Longitude(deg.E) Subionospheric Latitude(deg.N)

65 70 75 80 85 90 15 20 25 30 35 40

Propagation angle(deg.) Magnetic Latitude(deg.N) Subionospheric Longitude(deg.E)

45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.0 105.0 110.0 115.0 120.0 125.0 130.0 135.0 140.0 145.0 150.0 155.0 160.0 165.0 170.0 175.0 180.0

a)Propagation angle map in terms of Subionospheric Latitude and Longitude for Delhi. b)Scintillation observed from Delhi during 17:00-18:00UT on September 11, 2004. c)Propagation angle map in terms of Magnetic Latitude and Subionospheric Longitude for Delhi. Station: Delhi [ Latitude:28.58oN, Longitude: 77.21o E (geographic) ;Magnetic Latitude:24.93oN]

65 70 75 80 85 90 15 20 25 30 35 40

Subionospheric Longitude(deg.E) Subionospheric Latitude(deg.N)

SLIDE 26

Station: Shimla Period: August-October 2004 LT = UT + 05.17h Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

13UT-14UT 14UT-15UT 15UT-16UT 16UT-17UT

SLIDE 27

Station: Shimla Period: August-October 2004 LT = UT + 05.17h Subionospheric Latitude(deg.N) Subionospheric Longitude(deg.E)

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

17UT-18UT 18UT-19UT 19UT-20UT 20UT-21UT

SLIDE 28

Maximum Propagation Angle : 179.85o Zone: 26.34o to 28.02oN and 76.34o-77.68oE (geographic) ; 22.48 to 24.35oN(magnetic )

a)Propagation angle map in terms of Subionospheric Latitude and Longitude for Shimla. b)Scintillation observed from Shimla during 17:00-18:00UT on September 11, 2004. c)Propagation angle map in terms of Magnetic Latitude and Subionospheric Longitude for Shimla. LT = UT + 05.17h

⃝ S4 < 0.3 □ 0.3 ≤ S4 < 0.6 ∆ S4 ≥ 0.6

Station: Shimla [ Latitude:31.09oN, Longitude: 77.07o E (geographic) ;Magnetic Latitude:27.65oN]

(a) (b) (c) IGRF-9 (2000) IGRF-9 (2000)

Subionospheric Longitude(deg.E) Subionospheric Latitude(deg.N)

65 70 75 80 85 90 15 20 25 30 35 40

Propagation angle(deg.) Magnetic Latitude(deg.N) Subionospheric Longitude(deg.E)

45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.0 105.0 110.0 115.0 120.0 125.0 130.0 135.0 140.0 145.0 150.0 155.0 160.0 165.0 170.0 175.0 180.0

65 70 75 80 85 90 20 25 30 35 40

Subionospheric Latitude(Degrees) Subionospheric Longitude(Degrees)

SLIDE 29

FROM SCINTILLATION DATA ANAYSIS AND COMPARISON WITH THEORETICAL PROPAGATION ANGLE MAPS….

For stations with magnetic latitude within 25oN, enhanced scintillations due to

field-aligned propagation occur when the irregularities causing L-band scintillaltions are in decaying phase, in the region of maximum propagation angle corresponding to the station as long as it lies within the equatorial irregularity belt (±20o magnetic latitude).

For Bangalore and Agatti the zone of the maximum propagation angle is about the

magnetic equator where ambient ionization is low, the irregularities being field- aligned and the field has minimum curvature at the magnetic equator, the ray path traverses shorter path length through irregularities in this zone and they could not be viewed ‘end-on’. Hence no enhanced scintillation owing to field alignment were

bserved from these stations
For Shimla with magnetic latitude greater than 25oN, enhanced scintillation due to

field-aligned propagation has been observed not in the region of maximum propagation angle but in a region of high propagation angle within the zone of reception of the station which overlapped with the equatorial irregularity belt.

SLIDE 30

74 75 76 77 78 79 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 74 75 76 77 78 79 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 74 75 76 77 78 79 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

0.200 0.400 0.600 0.800 1.000

74 75 76 77 78 79 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

1.0

Time: 13-14UT 18.1-19.1LT Time: 14-15UT 19.1-20.1LT Time: 15-16UT 20.1-21.1LT Time: 16-17UT 21.1- 22.1LT

Station: PALAMPUR Date: April 02, 2014 SSN: 86

0.8

0.6

0.4 0.2 S4

Subionospheric Longitude (deg. E) Subionospheric Latitude (deg.N)

SLIDE 31

74 75 76 77 78 79 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

0.2 0.4 0.6 0.8 1.0

1.0 0.2 0.4 0.6

0.8

Station: PALAMPUR Date: April 02, 2014 SSN: 86

Time: 17-18UT 22.1-23.1LT

Time: 18-19UT 23.1-00.1LT Time: 19-20UT 00.1-01.1LT Time: 20-21UT 01.1-02.1LT Subionospheric Longitude (deg. E) Subionospheric Latitude (deg.N)

SLIDE 32

676869707172737475767778798081828384858687 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 676869707172737475767778798081828384858687 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.0 105.0 110.0 115.0 120.0 125.0 130.0 135.0 140.0 145.0 150.0 155.0 160.0 165.0 170.0 175.0 180.0

Propagation Angle (deg.) Subionospheric Latitude (deg.N) Subionospheric Longitude (deg. E) Subionospheric Longitude (deg. E) Magnetic Latitude (deg. N) Station: PALAMPUR

SLIDE 33

74 75 76 77 78 79 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

74 75 76 77 78 79 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 74 75 76 77 78 79 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 74 75 76 77 78 79 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Station: DELHI Date: April 10, 2013 SSN: 94

Time: 13-14UT 18.2-19.2LT

0.2 0.4

0.6 0.8

1.0 S4

Time: 14-15UT 19.2-20.2LT Time: 15-16UT 20.2-21.2LT Time: 16-17UT 21.2-22.2LT Subionospheric Longitude (deg. E) Subionospheric Latitude (deg.N)

SLIDE 34

74 75 76 77 78 79 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

0.2000 0.4000 0.6000 0.8000 1.000

74 75 76 77 78 79 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 74 75 76 77 78 79 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 74 75 76 77 78 79 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Station: DELHI Date: April 10, 2013 SSN: 94

Subionospheric Longitude (deg. E) Subionospheric Latitude (deg.N) Time: 17-18UT 22.2-23.2LT Time: 18-19UT 23.2-00.2LT

0.2 0.4 0.6 0.8 1.0 S4

Time: 19-20UT 00.2-01.2LT Time: 20-21UT 01.2-02.2LT

SLIDE 35

Conclusions

GPS scintillations observed from stations located poleward of

the equatorial ionization anomaly in the Indian longitude sector, i.e. outside the irregularity belt, observe intense scintillations only when the satellite ray-path is aligned along the geomagnetic field line i.e. when the satellite views the bubble ‘end-on’ and the region of maximum propagation angle for that particular station overlaps with the equatorial irregularity belt.

The algorithm developed in the paper can identify the outage

zones for reference stations in the Indian SBAS located within and outside the equatorial irregularity belt. This information will be useful for SBAS users.

SLIDE 36

Acknowledgements

The authors are grateful to International

Association of Geomagnetism and Aeronomy (IAGA) for providing the IGRF coeffecients.

The authors acknowledge the help of Mr.

Utsav Bhowmik in developing the algorithm. Thank you!

SLIDE 37

68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00 100.0 105.0 110.0 115.0 120.0 125.0 130.0 135.0 140.0 145.0 150.0 155.0 160.0 165.0 170.0 175.0 180.0

68697071727374757677787980818283848586 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

Station: DELHI Propagation Angle (deg.) Subionospheric Latitude (deg.N) Magnetic Latitude (deg. N) Subionospheric Longitude (deg. E) Subionospheric Longitude (deg. E)

SLIDE 38

75 76 77 78 79 80 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

0.2000 0.4000 0.6000 0.8000 1.000

75 76 77 78 79 80 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 75 76 77 78 79 80 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 75 76 77 78 79 80 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Time: 13-14UT 18.2-19.2LT Time: 14-15UT 19.2-20.2LT Time: 15-16UT 20.2-21.2LT Time: 16-17UT 21.2-22.2LT Subionospheric Latitude (deg.N) Subionospheric Longitude (deg. E)

Station: DELHI Date: September 09, 2004 SSN: 42

0.2 0.4 0.6 0.8 1.0

SLIDE 39

75 76 77 78 79 80 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

0.2000 0.4000 0.6000 0.8000 1.000

75 76 77 78 79 80 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 75 76 77 78 79 80 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 75 76 77 78 79 80 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

S4 Subionospheric Longitude (deg. E) Subionospheric Latitude (deg.N)

Station: DELHI Date: September 09, 2004 SSN: 42

Time: 17-18UT 22.2-23.2LT Time: 18-19UT 23.2-00.2LT Time: 19-20UT 00.2-01.2LT Time: 20-21UT 01.2-02.2LT

0.2 1.0 0.4 0.6 0.8