Association of major earthquakes (magnitude >= 6 Richter scale) with geomagnetic activity index KP during the period 2001-2007

A critical study of variation of geomagnetic activity index Kp for the period 2001-2007 have been made and its close association with major earthquakes (magnitude >= 6 Richter scale) is presented. From statistical analysis it is confirmed that when Kp touches 0 or 0+ values, major earthquakes take place within 48 hours. This is also explained considering the motion of the molten metal inside the outer core of earth.

Automated method for calculating the Dst-index based on the wavelet model of geomagnetic field variations

A method for calculating the geomagnetic activity index Dst (Dst-index) based on a wavelet model of geomagnetic field variations is proposed. The method allows values of the Dst-ndex to be automatically obtained with a 1-minute resolution. The method is tested using data from equatorial stations [1]. The paper describes a calculation algorithm and presents estimation results. The calculation results are compared with the classical approach and the Kyoto method [2]. It is shown that the proposed method allows values of the Dst index to be obtained in the on-line mode with an admissible error.

EPP-NO_<i>x</i> in Antarctic springtime stratospheric column: Evidence from observations and influence of the QBO

Observations from the Ozone Monitoring Instrument (OMI) on the Aura satellite are used to study the effect of energetic particle precipitation (EPP, as proxied by the geomagnetic activity index Ap) on the Antarctic stratospheric NO2 column in late winter-spring (Aug-Dec) during the years 2005–2017. We show that the polar (60° S–90° S) stratospheric NO2 column is significantly correlated with EPP throughout the Antarctic spring, until the breakdown of the polar vortex in November. The strongest correlation takes place during years with easterly phase of the quasi-biennial oscillation (QBO). We propose that the QBO affects the polar springtime EPP-NOx in two ways: firstly by modulating the amount of the primary NOx source, N2O, transported to the polar region. Secondly, the QBO affects the temperature of the polar vortex and thus the amount of denitrification occurring in the polar vortex, also verified from HNO3 observations from the Microwave Limb Sounder (MLS/Aura). Our results suggest that NOx produced by EPP significantly contributes to the stratospheric NO2 column at the time when the ozone hole is present in the Antarctic stratosphere. Based on our findings, we recommend that as chlorine activation continues to decrease in the Antarctic stratosphere, the total EPP-NOx should be accounted for in predictions of Antarctic ozone recovery.

Reassessing the Predictions of Sunspot Cycle 24

Predictions of sunspot cycle are important due to their space weather effects. Bhattet al.(2009) predicted sunspot cycle 24 (Maximum amplitude: 92.8±19.6; Timing:October 2012±4 months) using relative sunspot number (International Sunspot Number), and average geomagnetic activity indexaaconsidering 2008 as the year of sunspot minimum. Owing to the extended solar minimum till 2009, we re-examine our prediction model. Also, the newly calibrated international sunspot number reduces many discrepancies in the old dataset and is available from Solar Influences Data Center (SIDC) website. Considering 2009 as sunspot minimum year and newly calibrated international sunspot number, (i) The annual maximum amplitude of cycle 24 = 118.5±24.4 (observed = 113.3±0.1), (ii) A smoothed monthly mean sunspot number maximum in January 2014±4 months (observed in February 2014). Our prediction method appears to be a reliable indicator for the predictability of cycle 25.

A homogeneous aa index: 2. Hemispheric asymmetries and the equinoctial variation

Paper 1 (Lockwood et al., 2018) generated annual means of a new version of the aa geomagnetic activity index which includes corrections for secular drift in the geographic coordinates of the auroral oval, thereby resolving the difference between the centennial-scale change in the northern and southern hemisphere indices, aaN and aaS. However, other hemispheric asymmetries in the aa index remain: in particular, the distributions of 3-hourly aaN and aaS values are different and the correlation between them is not high on this timescale (r = 0.66). In the present paper, a location-dependant station sensitivity model is developed using the am index (derived from a much more extensive network of stations in both hemispheres) and used to reduce the difference between the hemispheric aa indices and improve their correlation (to r = 0.79) by generating corrected 3-hourly hemispheric indices, aaHN and aaHS, which also include the secular drift corrections detailed in Paper 1. These are combined into a new, “homogeneous” aa index, aaH. It is shown that aaH, unlike aa, reveals the “equinoctial”-like time-of-day/time-of-year pattern that is found for the am index.