Preprints
https://doi.org/10.5194/egusphere-2024-1692
https://doi.org/10.5194/egusphere-2024-1692
12 Jul 2024
 | 12 Jul 2024

Modulation of cosmic ray ground-level enhancements by solar wind stream interface: a case study

Olakunle Ogunjobi and William Tafon Sivla

Abstract. Ground level enhancements (GLEs) result from transient intensity increases in secondary cosmic ray particles detected by ground-based neutron monitors. Characterizing the temporal evolution of GLEs provides insight into particle acceleration mechanisms and interplanetary transport processes. The present study investigates the moderate intensity GLE 72 event on 10 September 2017, which fortuitously occurred during a solar wind stream interface (SI) region impacting the Earth's magnetosphere. We quantify how transient solar wind structures modulate the observed GLE pulse shape by combining multi-station neutron monitor observations with Monte Carlo particle transport models. Based on this analysis, we find that the turbulent magnetic field within the SI significantly enhances pitch angle scattering rates for energetic particles. In comparison to typical impulsive events, particle mean free paths declined by approximately 35 % during the 6-hour SI crossing. The stochastic acceleration caused by interactions with the disturbed magnetic fields resulted in higher particle intensities later in the event. According to these results, even moderate interplanetary disturbances can significantly alter transport conditions and alter the intensity-time profiles for GLEs. This further corroborates previous findings that the traditional classification of GLEs solely based on temporal characteristics, which may be obscured by transient propagation effects is superfluous. The study highlights the need to integrate multi-spacecraft solar wind observations into the interpretation of GLEs in order to disentangle intrinsic acceleration mechanisms from interplanetary modulation processes.

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Olakunle Ogunjobi and William Tafon Sivla

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-1692', Anonymous Referee #1, 26 Aug 2024
    • AC1: 'Reply on RC1', Olakunle Ogunjobi, 03 Sep 2024
      • RC3: 'Reply on AC1', Anonymous Referee #1, 16 Sep 2024
        • EC1: 'Reply on RC3', Andrew J. Kavanagh, 16 Sep 2024
        • AC3: 'Reply on RC3', Olakunle Ogunjobi, 08 Oct 2024
  • RC2: 'Comment on egusphere-2024-1692', Anonymous Referee #2, 16 Sep 2024
  • AC4: 'Comment on egusphere-2024-1692', Olakunle Ogunjobi, 15 Oct 2024
Olakunle Ogunjobi and William Tafon Sivla
Olakunle Ogunjobi and William Tafon Sivla

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Short summary
Our study probes how solar wind disturbances affect cosmic rays at Earth during solar eruptions. Increased cosmic rays during heightened solar wind suggest turbulence scatters and redistributes them, prolonging intensity. Understanding these effects is crucial for accurate cosmic ray data interpretation.