Abstract
Abstract The Carrington storm in 1859 September has been arguably identified as the greatest geomagnetic storm ever recorded. However, its exact magnitude and chronology remain controversial, while their source data have been derived from the Colaba H magnetometer in India. Here, we have located the Colaba 1859 yearbook, containing hourly measurements and spot measurements. We have reconstructed the Colaba geomagnetic disturbances in the horizontal component (ΔH), the eastward component (ΔY), and the vertical component (ΔZ) around the time of the Carrington storm. On their basis, we have chronologically revised the interplanetary coronal mass ejection transit time as ≤17.1 hr and located the ΔH peak at 06:20—06:25 UT, revealing a magnitude discrepancy between the hourly and spot measurements (−1691 nT versus −1263 nT). Furthermore, we have newly derived the time series of ΔY and ΔZ, which peaked at ΔY ≈ 378 nT (05:50 UT) and 377 nT (06:25 UT), and ΔZ ≈ −173 nT (06:40 UT). We have also computed their hourly averages and removed their solar quiet field variations in each geomagnetic component to derive their hourly disturbance variations (Dist) with latitudinal weighting. Our calculations have resulted in disturbance variations with latitudinal weighting of Dist Y ≈ 328 nT and Dist Z ≈ −36 nT, and three scenarios of Dist H ≈ −918, −979, and −949 nT, which also approximate the minimum Dst. These data may suggest preconditioning of the geomagnetic field after the August storm (ΔH ≤ −570 nT), which made the September storm even more geoeffective.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call