DOI: 10.5281/zenodo.17927681
title: Swarm-EMIC Research Project - EMIC database

description: This dataset comprises databases of electromagnetic ion cyclotron (EMIC) wave events detected by automated Pc1 wave finding algorithms developed by the VI3DLabs & University of Alberta team using Swarm 50 Hz magnetic field, 16 Hz electric field and 2 Hz Langmuir probe density datasets, as well as incorporating Canadian Space Agency CARISMA and NASA Van Allen Probes datasets. This dataset is published as a deliverable of the European Space Agency Swarm-EMIC project which aims to use Swarm datasets to investigate the impact of EMIC waves on energetic electron precipitation. A link to the project description can be accessed here: ttps://eo4society.esa.int/projects/swarm-emic/

The dataset is in CSV format with 2 possible formats for the EMIC wave confidence metric. The old format is a confidence score from 1-6, the new metric is a confidence matrix flagging specific conditions (e.g. Pc1 transverse wave energy; E/B fields corresponding to travelling Alfven wave; conjugate EMIC wave observations by CARISMA etc). The reason for the new format is to be able to flag multiple conditions simultaneously. 

If the file is a N x 25 or a N x 29 matrix, the EMIC wave flag is a confidence score; if it is a N x 31 or a N x 35 matrix, the EMIC wave flag is a confidence matrix. The confidence matrix files also have 'EB' in their filenames. The column values are defined below. 

tsBegin - EMIC event beginning (timestamp in datenum format)tsEnd - EMIC event ending (timestamp in datenum format)duration - EMIC event duration in secondsfCtr - event centre frequency in HzfBW - event bandwidth (full-width half maximum, or FWHM) in Hzellip - ellipticity (-1 for left-hand circular polarised, 0 for linear, +1 for right-hand circular polarised)minP2P - minimum peak-to-peak magnitude of the event (nT)medianP2P - median peak-to-peak magnitude of the event (nT)maxP2P - maximum peak-to-peak magnitude of the event (nT)BminCtr - the B-field minimum of the field line at the event centre (traced to the equator using IGRF)EMICband - EMIC band based on observed frequency and the traced estimated equatorial gyrofrequencies from BminCtr. Values are as follows: 0 = above H+ gyro, 1 = below H+ gyro, 2 = below He+ gyro, 3 = below O+ gyro, -1 = tracing failed/unknown bandMLTbegin - MLT at the beginning of the eventMLTctr - MLT at the centre of the eventMLTend - MLT at the end of the eventLmBegin - the McIlwain L-shell at the beginning of the eventLmCtr - Lm at centre of the eventLmEnd - Lm at end of the eventLstarBegin - L* at beginning of eventLstarCtr - L* at centre of the eventLstarEnd - L* at end of the eventgeoLatBegin - geographic latitude (in deg) at event beginninggeoLatEnd - geographic latitude (in deg) at event endgeoLonBegin - geographic longitude (in deg) at event beginninggeoLonEnd - geographic longitude (in deg) at event endcgmLatBegin - corrected geomagnetic (CGM) latitude (in deg) at beginning of event - only present in N x 29 and N x 35 data filescgmLatEnd - CGM latitude (in deg) at end of the event - only present in N x 29 and N x 35 data filescgmLonBegin - CGM longitude (in deg) at beginning of the event - only present in N x 29 and N x 35 data filescgmLonEnd - CGM longitude (in deg) at end of the event - only present in N x 29 and N x 35 data filesEMICconf - EMIC event confidence level - either a scalar confidence score or a N x 7 confidence matrix

The EMIC event confidence level ('EMICconf') is defined on a 1-6 scale as follows: 

1 - compressional Pc1 energy bounded from above and below by area of reduced power2 - transverse Pc1 energy bounded from above and below by area of reduced power3 - both compressional AND transverse Pc1 energy bounded from above and below by area of reduced power4 - as 3 but the centre frequency, lower and upper bounds (determined separately from half-maximum, i.e. 3dB either side of the peak) are within 0.5 Hz of each other5 - Pc1 event of at least level 2 is also conjugate with CARISMA ICM (100 Hz) ground magnetometers. Swarm and CARISMA FWHMs must overlap6 - Pc1 event of at least level 2 is also conjugate with Van Allen Probe satellite observations using EMFISIS fluxgate magnetometer (64 Hz). Swarm and VAP FWHMs must overlap

Where the EMIC wave flag is a confidence matrix, the elements of the matrix are defined by the last N x 7 elements within the file. Each of the 7 elements corresponds to specific conditions; multiple conditions may be true simultaneously. The 7 conditions are as follows: 

1st element - Pc1 energy in compressional mode2nd element - Pc1 energy in transverse mode3rd element - Pc1 energy in compressional and transverse mode matched within 0.5 Hz4th element - free-travelling Alfven wave confirmed with E- and B-fields5th element - Pc1 transverse-mode energy on Swarm AND conjugate CARISMA groundstation6th element - Pc1 transverse-mode energy on Swarm AND conjugate VAP-A B-field. The values here can be : 0 (no conjunction), 1 (Swarm-VAP conjunction), 2 (Swarm-VAP conjunction; Pc1 waves detected in both), or 3 (Swarm-VAP conjunction; Pc1 waves detected in both with matching frequencies/overlapping FWHM)7th element - Pc1 transverse-mode energy on Swarm AND conjugate VAP-B B-field. The values here can be : 0 (no conjunction), 1 (Swarm-VAP conjunction), 2 (Swarm-VAP conjunction; Pc1 waves detected in both), or 3 (Swarm-VAP conjunction; Pc1 waves detected in both with matching frequencies/overlapping FWHM)

This database will be expanded in subsequent releases with new data from the 3 Swarm spacecraft. Any changes to the processing algorithms and format will be reflected in the new version Description file. 

The ZIP file ('SwarmEMICscripts.zip') contains the Matlab and Python codes which were used to generate the database. The code utilises the IRBEM field tracing library: https://prbem.github.io/IRBEM/ as well as the aacgmv2 Python package (https://github.com/aburrell/aacgmv2). 

For any questions, please reach out to Dr Ivan Pakhotin (i.pakhotin@vi3dlabs.com) or Prof Ian R Mann (imann@ualberta.ca).