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NWRA Effective Smoothed Sunspot Numbers

:Product: NWRA 24h Effective SSN Analysis
:Issued: 2024-02-25 06:41 UT
#  Prepared by NorthWest Research Associates, Inc. 
#  Uses foF2 data from NOAA/NCEI.
#
#Hemisphere YYYYMMDD HH   SSNe     RMS    RMS%    #  Status
#---------- -------- --  ------  ------  ------  --- ------
 Global     20240225 06  114.99    1.25   20.12  332   GRN
 Northern   20240225 06  117.87    0.98   16.83  245   GRN
 Southern   20240225 06  100.60    1.76   23.96   67   YEL
#---------- -------- --  ------  ------  ------  --- ------
# Status: Green
# Hours to last foF2 observation: 0
#
Listings of past 5 hours:
Global SSNe
YYYYMMDD HH   SSNe     RMS    RMS%    #
-------- --  ------  ------  ------  ---
20240225 02  114.01    1.24   20.62  331
20240225 03  113.96    1.26   20.84  330
20240225 04  113.90    1.26   20.91  331
20240225 05  114.17    1.26   20.81  331
20240225 06  114.99    1.25   20.12  332
-------- --  ------  ------  ------  ---
Northern Hemisphere SSNe
YYYYMMDD HH   SSNe     RMS    RMS%    #
-------- --  ------  ------  ------  ---
20240225 02  116.30    1.00   17.05  244
20240225 03  116.36    1.00   17.21  244
20240225 04  116.46    0.99   17.17  244
20240225 05  117.01    0.98   16.81  244
20240225 06  117.87    0.98   16.83  245
-------- --  ------  ------  ------  ---
Southern Hemisphere SSNe
YYYYMMDD HH   SSNe     RMS    RMS%    #
-------- --  ------  ------  ------  ---
20240225 02  102.95    1.78   26.40   67
20240225 03  102.16    1.80   26.49   67
20240225 04  100.69    1.79   26.25   67
20240225 05   99.86    1.80   26.22   67
20240225 06  100.60    1.76   23.96   67
-------- --  ------  ------  ------  ---
 
Updated hourly at 40 minutes past the hour

The SSNe index presented on the NWRA website is calculated using the URSI coefficient-based model for foF2 commonly referred to as the URSI-88 model (Rush et al., 1989). The foF2 data used are provided from a global network of ionospheric sounders currently collected at the National Centers for Environmental Information (NCEI).

An SSNe index is generated once per hour for four different set of observed foF2: (1) all observations equatorward of 50 degrees geomagnetic latitude over the past 24 hours (SSNe24), (2) all observations equatorward of 50 degrees geomagnetic latitude over the past 6 hours (SSNe06), (3) all observations between +15 and +50 degrees geomagnetic latitude (NH SSNe24) over the past 24 hours, and (4) all observations between -15 and -55 degrees geomagnetic latitude (SH SSNe24) over the past 24 hours.

A more detailed description of the algorithms used and a review of the efficacy of using SSNe can be found in Secan and Wilkinson (1997).

NOTE: The international solar community has recalibrated and rescaled the sunspot number and refer to the new scaling as the V2.0 sunspot series. The foF2 model the SSNe estimate is calculated from was based on the V1.0 sunspot number series. Thus all SSNe values are inherently tied to the V1.0 scaling. If the software you plan to use SSNe with explicitly states that the input sunspot number must be consistent with the V2.0 sunspot series you should divide the SSNe by 0.7 to obtain the corresponding V2.0 value.

Rush, C., M. Fox, D. Bilitza, K. Davies, L. McNamara, F. Stewart, and M. PoKempner, Ionospheric Mapping: An Update of foF2 Coefficients, Telecommun. J., 56(179), 1989.

Secan, J.A. and P.J. Wilkinson, Statistical studies of an effective sunspot number, Radio Science, 32, 1717-1724, 1997.

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