Recent studies have shown that when a polar-orbiting satellite, in an altitude range similar to the Swarm satellites (ESA's Earth Observation constellation mission), passes the auroral oval, the latitude of the maximum polar electrojet (PEJ) encountered during the pass, as well as its intensity level, can be estimated by observing the absolute magnetic field intensity profile. The intensity of PEJ depends on the coupling of the solar wind to the magnetosphere, the state of the magnetosphere and the ionospheric electrical conductance, which in turn depends on the season, local time and the intensity of auroral particle precipitation. Each orbit of one of the Swarm satellites provides data from four passages of the auroral oval - two in each hemisphere. The location and intensity level of the polar electrojets can be derived from the Swarm measurements of the magnetic field strength at 1 Hz sampling, currently provided as the Swarm L1b product MAGx_LR_1B. Only the observed absolute magnetic field strengths and the satellite position are required, which means that the algorithm is independent of both attitude observations and L1b processing of the vector data. The derivation also needs input from a model allowing for along-orbit estimation of the magnetic field created in the ionosphere. Currently, magnetic field contributions for the core, lithosphere and large-scale magnetosphere are predicted by respective magnetic field models provided as products from the Swarm mission. Three levels of PEJ intensity are provided (green, yellow, and red) with corresponding peak current values in kA. The attributed intensity level is determined from the accumulative occurrence distribution of the PEJ intensities derived from the Swarm database. Green is assigned to PEJ intensity values that fit the lowest 80% of the PEJ intensity values in the statistical database, red is assigned to PEJ intensity values that fit the highest 0.8% of the PEJ intensity values in the statistical database, and yellow to values between these two groups. The rationale for this choice of PEJ intensity levels was that the occurrence distribution of the Kp value in the intervals Kp = 0-2, 3-4, and 5-9 during this period is similar. However, it should be underlined that individual PEJ intensity levels cannot be directly translated into the associated Kp level for a given local pass. Although the two are related, it is far from a one-to-one correspondence between the PEJ intensity and the Kp value. The Swarm Utilisation Analysis (SUA) PEJ dataset is structured in ASCII format with daily files. The data files follow the naming convention "SW_OPER_PNMXTMSSWE_YYYY-MM-DD," where SW stands for Swarm, OPER for operational, PNM for a product name (e.g., PEJ), X for Swarm satellite name (A, B, or C), TMS for time series, SWE for Space Weather, and YYYY, MM, DD for year, month, and day, respectively. The dataset can be accessed at ftp://isdcftp.gfz-potsdam.de/swarm/SUA/PEJ_TMS for all three Swarm satellites. Each SUA PEJ data file contains nine variables (from column 1 to column 9) and starts with a header line: mjd2000; date [YYYY-MM-DDThh:mm:ss]; orb num; lat [deg]; lon [deg]; mlat [deg]; mlt; color code; Peak current intensity [kA]. The variable definitions are as follows: mjd2000 (modified Julian day that starts at midnight of 01/01/2000); date (YYYY-MM-DDThh:mm:ss, where hh:mm:ss represents hour, minute, and seconds expressed in UTC); orb num (Swarm Orbit Counter); lat (geocentric latitude in degrees); lon (geocentric longitude in degrees); mlat (magnetic latitude, modified apex, in degrees); mlt (magnetic local time in decimal hours); color code (string values of green [g], yellow [y], and red [r]); Peak current intensity (in kiloamperes).
The Swarm (ESA's Earth Observation constellation mission) Level 2 time series of field-aligned and radial current densities along the orbit using the dual-satellite method for the Swarm lower satellite pair A and C are provided. Field-aligned current (FAC) density is derived by multiplying the radial current (IRC) density with the inclination angle of the geomagnetic field. This can be calculated for latitudes where the magnetic field is well inclined (|I| > 30°). In areas near the magnetic equator where the magnetic inclination angle is less than 30° (|I| < 30°), the FAC values are set to NaN. The radial current density can be calculated for the entire orbit, except for latitudes above 87° (near the poles), where both FAC and IRC values are set to NaN. It is important to note that for this time series provided here, the magnetic field data used for the dual-satellite method is not low-pass filtered with a 3-dB cutoff period of 20 seconds (corresponding to a wavelength of 150 km) as described in the "swarm-level-2-fac-dual-product-description" document. Additionally, FAC and IRC values are set to NaN when the integration area becomes smaller than 3e8 m^2, and no daily CDF files are produced if the along-track time difference between two Swarm satellites (A and C) exceeds 11 seconds. The data is provided in NASA CDF format and can be accessed at ftp://isdcftp.gfz-potsdam.de/swarm/OPER/Level2/FAC_TMS/Sat_AC/small_scale. The output variable description is available at https://swarmhandbook.earth.esa.int/catalogue/SW_FAC_TMS_2F.
Monthly gravity fields from Swarm A, B, and C, using the integral equation approach with short arcs. Software: GROOPS; Approach: Short-arc approach (Mayer-Gürr, 2006); Kinematic orbit product: IfG Graz: https://ftp.tugraz.at/outgoing/ITSG/satelliteOrbitProducts/operational/Swarm-1/kinematicOrbit/; Arc length: 45 minutes; Reference GFM: GOCO06s (Kvas et. al, 2021), monthly mean has been added back to the solution; Drag model: NRLMSIS2; SRP and EARP and EIRP models: Vielberg & Kusche (2020); Empirical parameters: + for non-gravitational accelerations (sum of Drag+SRP+EIRP+EARP): Bias per arc and direction; + for Drag: Scale per arc and direction; + for radiation pressure (sum of SRP+EIRP+EARP): Scale per day and direction; Non-tidal model: Atmosphere and Ocean De-aliasing Level 1B RL06 (Dobslaw et al., 2017); Ocean tidal model: 2014 finite element solution FES2014b (Carrere et al., 2015); Atmospheric tidal model: AOD1B RL06 atmospheric tides ; Solid Earth tidal model: IERS2010; Pole tidal model: IERS2010; Ocean pole tidal model: IERS2010 (Desai 2002); Third-body perturbations: Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn, following the JPL DE421 Planetary and Lunar Ephemerides (Folkner et al., 2014).
Phase A: roessler_pollino_locations_gfzpublication20100101_20120527_0_90.png roessler_pollino_locations_gfzpublication20100101_20120527_movie.avi Map with the locations of earthquake hypocentres during phase A (01/01/2010 - 27/05/2012). The yellow star shows the location of the main M5.2 earthquake on 25 October 2012. Day 0 corresponds to the start of the Pollino Seismic experiment on 2 November 2012. The system of normal faults on the surface are redrawn from [1]. Phase B: roessler_pollino_locations_gfzpublication20120528_20120731_0_90.png roessler_pollino_locations_gfzpublication20120528_20120731_movie.avi Map with the locations of earthquake hypocentres during phase B (28/05/2012 - 31/07/2012). The yellow star shows the location of the main M5.2 earthquake on 25 October 2012. Small grey dots: events during the phase A. Day 0 corresponds to the start of the Pollino Seismic experiment on 2 November 2012. The system of normal faults on the surface are redrawn from [1]. Phase C: roessler_pollino_locations_gfzpublication20120801_20121024_0_90.png roessler_pollino_locations_gfzpublication20120801_20121024_movie.avi Map with the locations of earthquake hypocentres during phase C (01/08/2012 - 24/10/2012). The yellow star shows the location of the main M5.2 earthquake on 25 October 2012. Small grey dots: events during the phases A, B. Day 0 corresponds to the start of the Pollino Seismic experiment on 2 November 2012. The system of normal faults on the surface are redrawn from [1]. Phase D: roessler_pollino_locations_gfzpublication20121025_20121212_0_90.png roessler_pollino_locations_gfzpublication20121025_20121212_movie.avi Map with the locations of earthquake hypocentres during phase D (25/10/2012 - 12/12/2012). The yellow star shows the location of the main M5.2 earthquake on 25 October 2012. Small grey dots: events during the phases A, B,C. Day 0 corresponds to the start of the Pollino Seismic experiment on 2 November 2012. The system of normal faults on the surface are redrawn from [1]. Phase E: roessler_pollino_locations_gfzpublication20121213_20121219_0_90.png roessler_pollino_locations_gfzpublication20121213_20121219_movie.avi Map with the locations of earthquake hypocentres during phase D (13/12/2012 - 19/12/2012). The yellow star shows the location of the main M5.2 earthquake on 25 October 2012. Day 0 corresponds to the start of the Pollino Seismic experiment on 2 November 2012. The system of normal faults on the surface are redrawn from [1]. Phase F.1: roessler_pollino_locations_gfzpublication20121220_20131231_0_90.png roessler_pollino_locations_gfzpublication20121220_20131231_movie.avi Map with the locations of earthquake hypocentres during phase F.1 (20/12/2012 - 31/12/2012). The yellow star shows the location of the main M5.2 earthquake on 25 October 2012. Day 0 corresponds to the start of the Pollino Seismic experiment on 2 November 2012. The system of normal faults on the surface are redrawn from [1]. Phase F.2: roessler_pollino_locations_gfzpublication20140101_20140910_0_90.png roessler_pollino_locations_gfzpublication20140101_20140910_movie.avi Map with the locations of earthquake hypocentres during phase F.1 (01/01/2013 - 10/09/2014). The yellow star shows the location of the main M5.2 earthquake on 25 October 2012. Day 0 corresponds to the start of the Pollino Seismic experiment on 2 November 2012. The system of normal faults on the surface are redrawn from [1].