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Interplanetary Coronal Mass Ejections, Associated Features, and Transient Modulation of Galactic Cosmic Rays

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Abstract

Interplanetary structures such as shocks, sheaths, interplanetary counterparts of coronal mass ejections (ICMEs), magnetic clouds, and corotating interaction regions (CIRs) are of special interest for the study of the transient modulation of galactic cosmic rays (GCRs). These structures modulate the GCR intensity with varying amplitudes and recovery-time profiles. It is known that ICMEs are mainly responsible for Forbush decreases in the GCR intensity. However, not all of the ICMEs produce such decreases in GCR intensity. We utilize GCR intensity data recorded by neutron monitors and solar-wind plasma/field data during the passage of ICMEs with different features and structures, and we perform a superposed-epoch analysis of the data. We also adopt the best-fit approach with suitable functions to interpret the observed similarities and differences in various parameters. Using the GCR-effectiveness as a measure of the cosmic-ray response to the passage of ICMEs, about half of the ICMEs identified during 1996 – 2009 are found to produce moderate to very large intensity depressions in GCR intensity. The ICMEs associated with halo CMEs, magnetic-cloud (MC) structures, bidirectional superthermal electron (BDE) signatures, and those driving shocks are 1.5 to 4 times more GCR effective than the ICMEs not associated with these structures/features. Further, the characteristic recovery time of GCR intensity due to shock/BDE/MC/halo-CME-associated ICMEs is larger than those due to ICMEs not associated with these structures/features.

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Acknowledgements

Useful catalogs of ICMEs/CMEs/magnetic clouds prepared and published/displayed on websites (especially by I.G. Richardson and H.V. Cane, N. Gopalswamy and R.P. Lepping) are highly appreciated. We acknowledge the use of solar and plasma/field data through NASA/GSFC OMNI Web interface. K. Röhrs and R.B. Hicks, PIs of the Kiel and Calgary neutron monitors, respectively, are also thanked for making the data available in usable format. Use of these data is acknowledged with gratitude. We also thank the reviewer for constructive and helpful comments.

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Authors and Affiliations

  1. Department of Physics, Aligarh Muslim University, Aligarh, 202 002, India

    Anand Kumar &  Badruddin

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  1. Anand Kumar
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  2. Badruddin
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Corresponding author

Correspondence to Badruddin.

Appendices

Appendix A

Table 7 Gaussian-fit parameters for the distribution of maximum solar-wind velocity [V max], central-peak value of V max [x c], width [w], full width at half maximum [w c], and the product x c w c during the passage of ICMEs of different GCR effectiveness.
Full size table
Table 8 Gaussian-fit parameters for the distribution of maximum magnetic field [F max], central-peak value of F max [x c], width [w], full width at half maximum [w c], and the product x c w c during the passage of ICMEs of different GCR effectiveness.
Full size table
Table 9 Gaussian-fit parameters for the distribution of maximum electric field [E max], central-peak value of E max [x c], width [w], full width at half maximum [w c], and the product x c w c during the passage of ICMEs of different GCR effectiveness.
Full size table

Appendix B

Figure 10
figure 10

Frequency distribution of maximum speed, [V max, km s−1] observed during the passage of ICMEs associated/not associated with (a) shocks, (b) BDEs, (c) magnetic clouds, and (d) halo CMEs. Gaussian best-fit curves representing the distribution of ICMEs are also shown in the figure. The central-peak values [x c] and full widths at half maximum [w c] obtained from the fits.

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Figure 11
figure 11

Frequency distribution of maximum magnetic-field vector [F max, nT] observed during the passage of ICMEs associated/not associated with (a) shocks, (b) BDEs, (c) magnetic clouds, and (d) halo CMEs. Gaussian best-fit curves representing the distribution of ICMEs are also shown in the figure. The central peak values [x c] and full widths at half maximum [w c] obtained from the fits.

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Figure 12
figure 12

Frequency distribution of maximum electric field, [E max, mV m−1] observed during the passage of ICMEs associated/not associated with (a) shocks, (b) BDEs, (c) magnetic clouds, and (d) halo CMEs. Gaussian best-fit curves representing the distribution of ICMEs are also shown in the figure. The central-peak values [x c] and full widths at half maximum [w c] obtained from the fits.

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Appendix C

Table 10 Gaussian-fit parameters for the distribution of maximum solar-wind velocity [V max], central-peak value of V max [x c], width [w], full width at half maximum [w c], and the product x c w c during the passage of ICMEs with different structures/features.
Full size table
Table 11 Gaussian-fit parameters for the distribution of maximum magnetic field [F max], central-peak value of F max [x c], width [w], full width at half maximum [w c], and the product x c w c during the passage of ICMEs with different structures/features.
Full size table
Table 12 Gaussian-fit parameters for the distribution of electric field [E max], central-peak value of E max [x c], width [w], full width at half maximum [w c], and the product x c w c during the passage of ICMEs with different structures/features.
Full size table

Appendix D

Figure 13
figure 13

Exponential fit and characteristic recovery time [τ, hours] during recovery of GCR-intensity depressions due to ICMEs of different GCR-effectiveness.

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Figure 14
figure 14

Exponential fit and characteristic recovery time [τ, hours] during recovery of GCR-intensity depressions due to ICMEs associated/not associated with shocks and bidirectional superthermal electron events (BDEs).

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Figure 15
figure 15

Exponential fit and characteristic recovery time [τ, hours] during recovery of GCR-intensity depressions due to ICMEs associated/not associated with magnetic cloud (MC) and halo CMEs.

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Kumar, A., Badruddin Interplanetary Coronal Mass Ejections, Associated Features, and Transient Modulation of Galactic Cosmic Rays. Sol Phys 289, 2177–2205 (2014). https://doi.org/10.1007/s11207-013-0465-7

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  • DOI: https://doi.org/10.1007/s11207-013-0465-7

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