Validating the LDi and LCi Indices in the Southern Hemisphere

Abstract

The validation of the Local Disturbance index (LDi) and its first time derivative Local Current index (LCi) is performed in the Southern Hemisphere. Two South African magnetic observatories, Hermanus and Hartebeesthoek contributed data for this study, and two South African power stations, Grassridge and Matimba, provided geomagnetically induced current (GIC) data. This validation focused on two major geomagnetic storms, Halloween and Saint Patrick's Day events that occurred in October 2003 and March 2015, respectively. The comparative evaluation of the LDi and LCi indices was executed with the help of the local horizontal component (H) and also comparing them to the global index SYM‐H. A direct comparison to measured GIC shows that LCi performs slightly better than dH/dt as a proxy for GIC. The comparison of the LDi 1‐hr magnetic disturbances values to ones calculated applying a Linear phase Robust Non‐Smoothing method to the H component yields a Pearson correlation coefficient R greater than 0.960 for different groups of magnetic storms based on intensity. The estimated SYM‐H index from LDi data showed a possible difference of about 300 nT from the published SYM‐H index values around 20:00 UT on 29 October 2003, during the Halloween storm. This study has shown that the LDi and LCi indices, developed in the Northern Hemisphere, can be calculated at similar latitudes in the Southern Hemisphere for studying local space weather conditions and now‐casting successfully local geomagnetic events.

Mid‐Latitude Double H‐Spikes: Their Properties and Signatures in Different Geomagnetic Indices

“…(2022) showed also GICs measured at Grassridge substation (33.7°S, 25.6°E), located at midlatitude in South Africa (near the Hermanus magnetic observatory), in the period 29–30 October (see Figure 2 of Nahayo et al. (2022)). As can be seen in that figure, significant GICs (∼10 A) were recorded during the double H‐spike with peak at 6:58 UT on 29 October and also during the double H‐spike on 30 October mentioned above.…”

“…Excess heating in a transformer occurred on 30 October 2003 at 20:07 UT (Pulkkinen et al, 2005;Wik et al, 2009), just 11 min after the peak of a double H-spike of 349 nT intensity occurred at 19:56 UT on 30 October (Table 1). Recently, Nahayo et al (2022) showed also GICs measured at Grassridge substation (33.7°S, 25.6°E), located at midlatitude in South Africa (near the Hermanus magnetic observatory), in the period 29-30 October (see Figure 2 of Nahayo et al (2022)). As can be seen in that figure, significant GICs (∼10 A) were recorded during the double H-spike with peak at 6:58 UT on 29 October and also during the double H-spike on 30 October mentioned above.…”

“…Recently, Nahayo et al. (2022) showed also GICs measured at Grassridge substation (33.7°S, 25.6°E), located at midlatitude in South Africa (near the Hermanus magnetic observatory), in the period 29–30 October (see Figure 2 of Nahayo et al. (2022)).…”

Neural Networks for Operational SYM‐H Forecasting Using Attention and SWICS Plasma Features

“…For the index, we retrieve the data from the OMNI_HRO_5MIN data set. Meanwhile the SYM-H can be obtained from OMNI for the training and testing of the model, for its operational deployment we compute it in real time following the procedure proposed by Nahayo et al (2022). For the IMF data we use the level-2 data measured by the Magnetic Field Experiment (MAG) instrument on ACE.…”

Using Application Usability Levels to support tracking the health of Heliophysics

“…Phase 3 projects have completed validation and are being implemented into operational solutions. The AUL framework has been employed in the development and validation of the LDi and LCi geomagnetic indices (Cid et al, 2020;Nahayo et al, 2022). These new indices were developed jointly by researchers and industry users for nowcasting local geomagnetic disturbances (LDi) and for geomagnetically induced current risk (LCi).…”