S4 and Sigma Phi Maps – Version 1.0
Release Date: 2026-05-01
For additional information about the EMBRACE Space Weather Program, please visit:
http://www2.inpe.br/climaespacial/
OVERVIEW
This directory contains gridded ionospheric scintillation maps generated from GNSS observations collected by the scintillation monitoring networks operated by:
- EMBRACE/INPE
- IBGE
- INCT-GNSS-NavAer/UNESP
- CBJLSW/NSSC/CAS
The maps represent the spatial distribution of two ionospheric scintillation parameters:
- S4 Index — Amplitude scintillation index (dimensionless)
- Sigma Phi (σφ) — Phase scintillation index (radians)
DIRECTORY STRUCTURE
maps/
└── parameter/
└── year/
└── doy/
└── data files
where:
parameter : map type (s4 or sigma_phi)
year : observation year
doy : day of year (001–366)
data files: map files corresponding to a specific epoch
FILE NAMING CONVENTION
Map files follow the format: PARAMETERMAP_YYYYMMDD_HHMM.txt
where:
PARAMETER : S4 (S4 map) or PHI (Sigma Phi map)
YYYY : year (4 digits)
MM : month (2 digits)
DD : day (2 digits)
HH : hour (UTC)
MM : minute (UTC)
Examples:
S4MAP_20260101_0000.txt
PHIMAP_20260101_0000.txt
GRID DESCRIPTION
Each file contains a two-dimensional regular geographic grid represented as an ASCII matrix.
Geographic Coverage
Longitude range: -140° to -20°
Latitude range : -60° to 50°
Grid Organization
- Rows correspond to latitude values.
- Columns correspond to longitude values.
- Grid values represent the estimated scintillation parameter at each ionospheric pierce point.
Missing Data
Unavailable or invalid grid cells are represented by: -1
Users should convert these values to NaN (or an equivalent missing-data flag) before performing analyses.
S4 MAPS
S4 maps represent the spatial distribution of the ionospheric amplitude scintillation index.
Units: Dimensionless
Typical Interpretation
S4 < 0.50 Weak scintillation
0.50 ≤ S4 < 0.80 Moderate scintillation
S4 ≥ 0.80 Strong scintillation
SIGMA PHI MAPS
Sigma Phi (σφ) maps represent the spatial distribution of the ionospheric phase scintillation index.
Units: Radians
Typical Interpretation
σφ < 0.40 Weak phase scintillation
0.40 ≤ σφ < 0.70 Moderate phase scintillation
σφ ≥ 0.70 Strong phase scintillation
STATIONS COORDINATES:
|--------------------------------------------------------------------------------------------------------------------|
|fullname |code |longitude |latitude |network |
|---------------------|-------------------------------------|--------------|-----------------------------------------|
|Alfredo Marcondes |STAF |-51.414574 |-21.954102 |INCT GNSS-NavAer/UNESP |
|Álvares Machado |STAV |-51.49987 |-22.09647 |INCT GNSS-NavAer/UNESP |
|Aquidauana |MSAQ |-55.671165 |-20.452944 |EMBRACE / IBGE /INPE |
|Araguatins |STAR |-48.073338 |-5.651169 |INCT GNSS-NavAer/UNESP |
|Bacabal |MABB |-44.815722 |-4.2409592 |EMBRACE / IBGE /INPE |
|Balneário Rincão |STBR |-49.21393 |-28.826715 |INCT GNSS-NavAer/UNESP |
|Boa Vista |STBV |-60.697174 |2.8337984 |INCT GNSS-NavAer/UNESP |
|Botucatu |SPBO |-48.4323 |-22.852467 |INCT GNSS-NavAer/UNESP |
|Cachoeira Paulista |STC1/STCP |-45.014732 |-22.702599 |INCT GNSS-NavAer/UNESP |
|Colider |STCL |-55.448093 |-10.81897 |INCT GNSS-NavAer/UNESP |
|Cuiabá |STCB |-56.06989 |-15.555245 |INCT GNSS-NavAer/UNESP |
|Curitiba |STCT |-49.236618 |-25.456932 |INCT GNSS-NavAer/UNESP |
|Eusébio |CEEU |-38.4246 |-3.87994 |EMBRACE / IBGE /INPE |
|Fortaleza |UFBA/FRTZ |-38.577633 |-3.744554 |INCT GNSS-NavAer/UNESP |
|Ilhéus |STIL |-39.1724 |-14.796632 |INCT GNSS-NavAer/UNESP |
|Inconfidentes |INCO |-46.328114 |-22.318548 |INCT GNSS-NavAer/UNESP |
|Ji-Paraná |ROJI |-61.9597 |-10.8639 |EMBRACE / IBGE /INPE |
|Lins |SPLI |-49.733696 |-21.665205 |INCT GNSS-NavAer/UNESP |
|Manaus |STMN |-59.974903 |-3.1101797 |INCT GNSS-NavAer/UNESP |
|Maringá |PRMA |-51.938423 |-23.409689 |INCT GNSS-NavAer/UNESP |
|Monte Carmelo |STMC |-47.5238 |-18.724026 |INCT GNSS-NavAer/UNESP |
|Natal |STNT/RNNA |-35.196213 |-5.8405857 |INCT GNSS-NavAer/UNESP |
|Palmas |PALM |-48.3113 |-10.199649 |INCT GNSS-NavAer/UNESP |
|Pirapozinho |STPZ |-51.425987 |-22.24089 |INCT GNSS-NavAer/UNESP |
|Porto Alegre |POAL |-51.119682 |-30.073896 |INCT GNSS-NavAer/UNESP |
|Presidente Epitácio |STPE |-52.111637 |-21.785223 |INCT GNSS-NavAer/UNESP |
|Presidente Prudente |PRU2/MOR3/PPT5/PRU4/CTAS |-51.407078 |-22.122038 |INCT GNSS-NavAer/UNESP |
|Recife |STRE |-34.952946 |-8.053972 |INCT GNSS-NavAer/UNESP |
|Rosana |ROSA |-52.952087 |-22.523304 |INCT GNSS-NavAer/UNESP |
|Santa Helena |STSH |-54.344364 |-24.846996 |INCT GNSS-NavAer/UNESP |
|Santarém |PASM |-54.7289 |-2.42797 |EMBRACE / IBGE /INPE |
|São João da Boa Vista|STSJ |-46.79223 |-21.997086 |INCT GNSS-NavAer/UNESP |
|São José dos Campos |SJC1/SJCE/SJCU |-45.861057 |-23.20806 |INCT GNSS-NavAer/UNESP |
|São Luis |SLMA |-44.21229 |-2.593464 |INCT GNSS-NavAer/UNESP |
|Senhor do Bomfim |STSB |-40.146843 |-10.444889 |INCT GNSS-NavAer/UNESP |
|Sorriso |MTSR |-55.727413 |-12.545235 |EMBRACE / IBGE /INPE |
|Uruaçu |GOUR |-49.1436 |-14.5092 |EMBRACE / IBGE /INPE |
|Vitória da Conquista |BAVC |-40.8027 |-14.8883 |EMBRACE / IBGE /INPE |
|---------------------|-------------------------------------|--------------|-----------------------------------------|
DATA SOURCES
Scintillation Data Usage and Acknowledgment Guidelines
Institutions and Operators:
- INCT-GNSS-NavAer/UNESP (National Institute of Science and Technology – GNSS NavAer/São Paulo State University Julio de Mesquita Filho)
Operator: UNESP
- EMBRACE/IBGE/INPE (Brazilian Studies and Monitoring of Space Weather/Brazilian Institute of Geography and Statistics/National Institute for Space Research)
Operator: EMBRACE/INPE and IBGE
- CBJLSW/NSSC/CAS (Cina-Brasil Joint Laboratory for Space Weather/National Space Science Center/Chinese Academy of Sciences)
Operator: EMBRACE/INPE and CBJLSW/NSSC/CAS
Acknowledgment Suggestion:
The authors would like to thank the scintillation data network composed of instruments operated by INCT/UNESP, EMBRACE/INPE/IBGE, and NSSC/CAS. We thank EMBRACE/INPE of MCTI for their coordination and data provision and express our gratitude to all contributing institutions for their support in maintaining and sharing this valuable scientific resource.
Acknowledgement to the National Institute of Science and Technology for GNSS in Support of Air Navigation (INCT-GNSS-NavAer), funded by CNPq (465648/2014-2), FAPESP (2017/50115-0), and CAPES (88887.137186/2017-00).
Note: INCT-GNSS-NavAer was financed by CNPq, FAPESP and CAPES. The following publications are advised for citation: DOIs: https://doi.org/10.1590/jatm.v14.1249, https://doi.org/10.1590/jatm.v15.1288.
Version: 1.0
Dataset: S4 and Sigma Phi Gridded Scintillation Maps
Maintained by: EMBRACE/INPE and collaborating institutions.