Real-Time Model of the Ionospheric Electric Fields

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The equatorial ionospheric eastward electric field (EEF) is predicted on a real-time basis using the solar wind data from the Deep Space Climate Observatory (DSCOVR) satellite. During times of outages in DSCOVR data or problems with the data, this application may instead use the data from the NASA/ACE spacecraft, as provided by the NOAA's Space Weather Prediction Center. The web application can also be used to calculate the EEF for all longitudes from 01-01-1995 to present. The web application uses a transfer function model to predict the EEF variation from solar wind data and a climatological model to account for the quiet day variations of EEF. More details of the model and data processing are available with the links on the left side.

Prompt Penetration Equatorial Electric Field Model

Wind driven currents in the ionosphere coupled with the Earth's magnetic field produce the Equatorial Electric Field (EEF), which is responsible for driving many interesting ionospheric phenomena. The EEF is known to be highly variable from day to day, primarily as a result of solar wind electric fields penetrating from high latitudes to the equator, in addition to variabilities in the neutral winds coming from below. This work realistically models the time variations coming from the solar wind, which are mapped from interplanetary electric field (IEF) data through a transfer function model. The transfer function was derived from 8 years of IEF data from the ACE satellite, radar data from JULIA, and magnetometer data from the CHAMP satellite. This model also provides the climatology of the EEF, which is based on six years of magnetometer measurements from the CHAMP satellite. The model accepts as input a time and location and produces the best estimate of the EEF for those parameters.

Fig 1

References: 

Manoj, C., S. Maus, and P. Alken (2013), Long-period prompt-penetration electric fields derived from CHAMP satellite magnetic measurements, J. Geophys. Res. Space Physics, 118, 5919–5930, doi:10.1002/jgra.50511. 

Manoj, C., and S. Maus (2012), A real-time forecast service for the ionospheric equatorial zonal electric field, Space Weather, 10, S09002, doi:10.1029/2012SW000825. 

Manoj, C., S. Maus, H. Lühr, and P. Alken (2008), Penetration characteristics of the interplanetary electric field to the daytime equatorial ionosphere, J. Geophys. Res., 113, A12310, doi:10.1029/2008JA013381. 
 

We use the quiet time F region equatorial vertical drift model by Scherliess and Fejer (1999) for the climatological part of the real time calculator. The Scherliess and Fejer (1999) model describes the diurnal and seasonal variations in the ionospheric vertical drift for all longitudes and for all solar flux conditions. The model was derived from the incoherent scatter radar observations at Jicamarca and Ion Drift Meter observations by the Atmospheric Explorer E satellite. The vertical drift is converted to the equatorial ionospheric east ward electric field by multiplying it with the magnetic field strength along the dip equator determined from the CHAMP data (Luhr et al., 2004).


References: 

Scherliess, L. and Fejer, B.G. (1999). Radar and satellite global equatorial F region vertical drift model. Journal of Geophysical Research 104(A4): doi: 10.1029/1999JA900025. 

Luhr, H., S. Maus, and M. Rother (2004), Noon-time equatorial electrojet: Its spatial features as determined by the CHAMP satellite. Journal of Geophysical Research 109 A01306: doi: 10.1029/2002JA009656.

Real-time data from the ACE satellite:

  • The interplanetary electric field (also known as the solar wind electric field) is calculated from the interplanetary magnetic field and solar wind velocity. We use the data from the Deep Space Climate Observatory (DSCOVR) satellite. DSCOVR orbits the L1 libration point which is Help 1.5 million kilometers from the Earth, facing the sun. Due to large distance of DSCOVR from the earth in the upstream direction, the data provides around 1 hour of advance information about the solar wind condition. The real-time interplanetary data are obtained from the NOAA’ s Space Weather Prediction Center . The data are fetched every 1 minute and processed for propagation delay and errors.
  • The model requires the IEF data to be propagated from the satellite position to the bow shock nose of the Earth’s magnetosphere. For the real-time calculator,eef for any we assume that the solar wind travels at a constant speed along the Sun-Earth line to the magnetosphere (t_delay = delta X / V), where delta X is the distance between ACE satellite and the magnetosphere’s bow shock nose along the Sun-Earth line, and V is the solar wind velocity.
  • The real-time calculator can also be used to calculate the EEF for any date from 1995 to present. For dates older than two months from the present, we use the interplanetary data from the OMNI website. The data is derived from ACE, Wind, IMP 8 and Geotail satellites and is time-shifted to the Earth's bow shock nose using a combination of minimum variance and cross-product phase front normal determination techniques.
  • The solar flux data for the climatological model is derived from the SWPC data service. The model uses the 81-day moving average of F10.7 cm solar flux.

The real-time model is not indented to wholly represent the Equatorial Ionospheric electric field. Here are some of the limitations of the model:

  • We do not consider the electric field effects from
    • Terrestrial weather
    • Disturbance dynamo effect
  • Transfer function assumes that the magnetosphere acts as a linear, band-pass filter of the solar wind electric field. While this simple approximation accurately represents the prompt penetration effect for the majority of the days, the model can significantly differ from the data during and immediately after a major geomagnetic storm.
  • The actual variations in the quiet day EEF variations can differ from the climatological model by up to 0.3 mV/m on any day.
  • The propagation delay estimate relies on only the solar wind velocity. It does not take into account either the orientation of the IMF or the displacement of ACE satellite away from the Sun-earth line.
  • JULIA radar data: The Jicamarca Radio Observatory is a facility of the Instituto Geofísico del Perú operated with support from the NSF Cooperative Agreement ATM-0432565 through Cornell University.
  • NASA's OMNIWeb group for the Solar Wind data
  • NOAA's Space Weather Prediction Center for the f107 and the real-time ACE and DSCOVR data sets
  • Ludger Scherliess and Bela Fejer for the Climatological model
Usage instructions
  • Dates should be later than 1995-01-01 (YYYY-MM-DD)
  • Longitude should be between -180 to 180. 
  • Number of days should be between 1 and 5.
     
  • Advanced Options (new)
    • Auto: Use SWPC’s RTSW data for the present time to approximately 1 month back. For earlier data, it switches to quality-controlled data from NASA’a OMNI website.
    • ACE RTSW: Always use ACE RTSW data (1995 to present)
    • DSCOVR RTSW: Always use DSCOVR RTSW data (2016 to present)
Data download
  • Use the “chart options” to download the data in CSV format.
     
Programmatic access


Description of the optional query parameters. 
 

  • month = month of the year (1-12). The default is the current month.
  • day = day of the month. The default is the current day.
  • year = year (int) (1995 - present). The default is the current year
  • utc = start time in UTC hours. The default is the current time.
  • nDays = Time length of the data required in decimal days (0.125 - 5.0). When this is not specified AND no user start time is specified, data for current time to the end of the current prediction is returned. When the user time is specified and nDays is not specified, nDays will have the default value of 0.125 ( 3 hours). When the user-specified date + nDays exceeds the end of the prediction time, the data are plotted only till the end of the prediction time.
  • deltalong = longitude interval in decimal degrees. The value should be between 1 and 359. The default is 18 degrees.
  • startlong = first longitude for data. The default is 0 degrees.
  • comp = parameters to be printed. "pp" - prompt penetration only. "cl" - climatology only. "all" - all the components. The default is "pp" .
About


The web application and the models run on Google App Engine. Latest update : Oct 2024. Comments, suggestions and help requests to manoj.c.nair@noaa.gov