Study of the development and mechanism of large amplitude decreases in cosmic ray intensity during geomagnetic disturbances in the magnetosphere
Introduction
Disturbances in the geomagnetic field of the magnetosphere (Geomagnetic storms) and sudden disturbances (decreases) in the cosmic ray intensity (e.g., Forbush decreases) are observed together during the passage of interplanetary structures associated with the occurrence of coronal mass ejections (e.g., see, Badruddin et al., 1986, Venkatesan and Badruddin, 1990, Cane, 2000, Belov et al., 2001, Blanco et al., 2013, Arunbabu et al., 2013). However, the magnitudes of geomagnetic storms and Forbush decreases are not proportional to each other. Although the sources of the two phenomena may be the same, the generation mechanism of the two phenomena are different (e.g., Kudela and Brenkus, 2004, Kane, 2010, Badruddin and Kumar, 2015, Aslam and Badruddin, 2017).
Galactic cosmic rays (GCR) are high energy charged particles that enter the magnetic environment of the Sun (Heliosphere) from the outer space (Chowdhury et al., 2016, López-Comazzi and Blanco, 2020). The heliosphere is filled with solar plasma and the magnetic field carried outward by the solar wind blowing from the Sun. Travelling through this region from the outer heliosphere towards the Earth and Sun, these charged cosmic ray particles are affected by the presence of plasma and field in the interplanetary space. This result in variations of GCR intensity at various time scales, notably ~11-years and ~22-year periods (see, Potgieter, 2013, Aslam and Badruddin, 2015, Chowdhury and Kudela, 2018; and the references therein). However, in addition to these long-term variations, short-time variations (both periodic and non-periodic) are observed in GCR intensity (see, Dunzlaff et al., 2008, Singh et al., 2012, Kudela and Sabbah, 2016, Chowdhury et al., 2016, Poblet and Azpilicueta, 2018, López-Comazzi and Blanco, 2020, Oloketuyi et al., 2020). One of the prominent non-periodic short-time variations frequently observed is the so-called Forbush decrease; a sudden decrease in the GCR intensity of a few per cent magnitudes within a period of about one day followed a slow gradual recovery extending up to several days. These decreases are related to changes in plasma and field conditions in the interplanetary space. Changes in the plasma and field conditions observed in the interplanetary space are mainly due to two emissions of different nature; high-speed solar wind streams (HSS) from the coronal holes with open magnetic field lines and coronal mass ejections (CMEs) with closed magnetic field structures. Ejected from certain regions of the solar atmosphere and propagating in interplanetary space they evolve into two different types of large-scale interplanetary structures, corotating interaction regions (CIRs) and interplanetary manifestations of CMEs (ICMEs).
These two types of large-scale structures (CIRs and ICMEs) with distinct structures and plasma/field properties not only produce disturbances in GCR intensity (e.g., Lockwood, 1971, Mavromichalaki et al., 2003, Mavromichalaki et al., 2011, Modzelewska and Alania, 2012, Papaioannou et al., 2010, Papaioannou et al., 2020, Kumar and Badruddin, 2014, Badruddin and Kumar, 2016) but also generate disturbances in the geomagnetic activity in the near-Earth Space. The disturbances generated by CIRs in GCR intensity are in general, slowly varying of relatively smaller amplitudes and corotating in nature (see McKibben et al., 1999, Dumbović et al., 2012, Guo and Florinski, 2014, Luo et al., 2020). However, the ICME generated disturbances in GCR intensity are fast of larger amplitude and transient in nature (e.g., Iucci et al., 1989, Singh and Badruddin, 2007, Dorotovič et al., 2008, Richardson and Cane, 2011, Arunbabu et al., 2015, Belov et al., 2015, Bhaskar et al., 2016).
Individual transient decreases in GCR intensity, generally known as Forbush decreases (Forbush, 1937), are of different depth (magnitude of decrease) take different time to reach their minimum intensity level (different decrease duration) and take different time to reach normal intensity level (different recovery time). Study of Forbush decrease precursors along with interplanetary magnetic field and solar wind parameters can be useful to understand the relevance of Forbush decreases in space weather predictions, and also the physics of the transient variations (like FDs) in the GCR intensity (e.g., see, Kudela et al., 2000, Dorman, 2005, Chertok et al., 2018, Badruddin et al., 2019).
Although many studies in the past; both theoretical/modeling (Nishida, 1982, Kadokura and Nishida, 1986, Chih and Lee, 1986, le Roux and Potgieter, 1991, Luo et al., 2017) and observational (Lockwood et al., 1991, Badruddin et al., 1991, Belov et al., 2014, Belov et al., 2015, Badruddin et al., 2019) have attempted to understand this phenomenon of Forbush decrease (FD), opinions are still divided about the relative importance of different structures in ICMEs (shock/sheath/ejecta/magnetic clouds) in producing Forbush decreases (e.g., Zhang and Burlaga, 1988, Dasso et al., 2005, Reames et al., 2009, Yu et al., 2010, Petukhova et al., 2019). It is also to be established with certainty which interplanetary plasma/field parameter/function best correlates with the amplitude of Forbush decrease (Mavromichalaki et al., 2011, Melkumyan et al., 2019). Moreover, the physical process playing the dominant role in the phenomena of Forbush decreases still requires a general agreement (see, also Cane, 2000, Luo et al., 2017). It is also be established with certainty whether all the large amplitude Forbush decreases are due to shock associated ICMEs or some of them can be due to isolated ejecta/magnetic cloud only.
Recently, Fadaaq and Badruddin (2021) have studied the transient modulation of galactic cosmic rays. For this purpose, using superposed epoch analysis, they analyzed the cosmic ray intensity data and solar wind plasma/field parameters with reference to ICMEs associated/not-associated with shock and ICMEs having magnetic cloud/non-magnetic cloud structure. Their results are consistent with the hypothesis that transient decrease in cosmic ray intensity is mainly due to the turbulent shock/sheath region preceding the ICME and the decrease due to ICME without shock/sheath structure, if any, is small.
Present work is further attempt to understand the transient (Forbush) decrease phenomena better. For this purpose, we identified large-amplitude (≥5%) FDs with clear time profile. In this work, we use superposed epoch analysis to analyze the cosmic-ray neutron monitor data together with solar wind plasma/field data with reference to onset of selected Forbush decreases of different amplitude, decrease and recovery time. Moreover, for our analysis, we analyzed some additional solar wind plasma/field parameters (and their derivatives), compared to earlier studies (e.g., see Fadaaq and Badruddin, 2021 and the references therein).
Section snippets
Data and analysis
We isolated large-amplitude decreases from the neutron monitor records using Oulu neutron monitor (https://cosmicrays.oulu.fi/; 65.05°N, 25.47°E, local vertical geomagnetic cutoff rigidity is about 0.8 GV; see Usoskin et al. 2001) 1-hour resolution data plots for solar cycles 23 and 24 with following criteria: (a) The events show a clear profile of typical Forbush-like decrease with a fast decrease (of different decrease time) and smooth slow recovery (of different recovery durations) and free
Results and discussions
The superposed epoch analyzed results of the hourly GCR intensity (in %), solar wind velocity V (kms−1), IMF vector magnitude F (nT), RMS standard deviation in V [σV (kms−1)], RMS standard deviation in F [σF (nT)], the products [FV.10−3 (mVm−1)], and the product (σF.σV) are plotted in Fig. 1. In this figure epoch (zero hour) corresponds to the onset of selected 29 large-amplitude Forbush decreases. The solid line is superposed epoch result of 29 FD events and the shaded area indicates standard
Conclusions
The analysis of the selected 29 large FD events (≥5%) leads us to the following conclusions.
The onset of large-amplitude FDs coincides the shock arrival time during the passage of shock-sheath-ICME structure. Moreover, the major part of the decrease happens during the passage of magnetically turbulent sheath region in which σF is significantly enhanced, consistent with the earlier findings.
Durations of the main phase of FDs are quite variable from event to event. Our analysis, based on the
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This project was funded by the Deanship of Scientific Research (DSR) at King Abdulaziz University, Jeddah, under grant no. G: 354-130-1441. The authors, therefore, acknowledge with thanks DSR for technical and financial support. The authors thank the Station Manager of the Oulu neutron monitor (Ilya Usoskin) for making available the neutron monitor data (https://cosmicrays.oulu.fi). We acknowledge with thanks the use of the ICME catalog of I. G. Richardson and H.V. Cane
References (64)
- et al.
What determines the magnitude of Forbush decreases?
Adv. Space Res.
(2001) - et al.
Large scale MHD properties of interplanetary magnetic clouds
Adv. Space Res.
(2005) - et al.
Cosmic ray decreases and geomagnetic activity: list of events 1982–2002
J. Atmos. Solar-Terr. Phys.
(2004) - et al.
Applications and usage of the real-time neutron monitor database
Adv. Space Res.
(2011) - et al.
Short-term variations of cosmic-ray intensity and flare related data in 1981–1983
New Astron.
(2003) - et al.
Comparison between statistical properties of Forbush decreases caused by solar wind disturbances from coronal mass ejections and coronal holes
Adv. Space Res.
(2019) - et al.
Dependence of the 27-day variation of cosmic rays on the global magnetic field of the Sun
Adv. Space Res.
(2012) - et al.
27-day variation in solar-terrestrial parameters: Global characteristics and an origin based approach of the signals
Adv. Space Res.
(2018) - et al.
High-rigidity Forbush decreases: due to CMEs or shocks?
Astron. Astrophys.
(2013) - et al.
How are Forbush decreases related to interplanetary magnetic field enhancements?
Astron. Astrophys.
(2015)
Coronal mass ejections and non-recurrent Forbush decreases
Solar Phys.
Galactic cosmic ray density variations in magnetic clouds
Solar Phys.
Relative contribution of the magnetic field barrier and solar wind speed in ICME-associated Forbush decreases
Astrophys. J.
Coronal mass ejections and Forbush decreases
Space Sci. Rev.
A perturbation approach to cosmic ray transients in interplanetary space
J. Geophys. Res.
Quasi-periodicities in cosmic rays and time lag with the solar activity at a middle latitude neutron monitor: 1982–2017
Astrophys. Space Sci.
A study of heliospheric modulation and periodicities of galactic cosmic rays during cycle 24
Solar Phys.
Space weather and dangerous phenomena on the Earth: Principles of great geomagnetic storms forecasting by online cosmic ray data
Ann. Geophys.
On 17–22 January 2005 Events in Space Weather
Solar Phys.
An analytical diffusion-expansion model for Forbush decreases caused by flux ropes
Astrophys. J.
Cosmic ray modulation by different types of solar wind disturbances
Astron. Astrophys.
Observations of recurrent cosmic ray decreases during solar cycles 22 and 23
Ann. Geophys.
Study of transient modulation of galactic cosmic rays due to interplanetary manifestations of coronal mass ejections: 2010–2017
Astrophys. Space Sci.
Cited by (3)
Space weather monitoring with Health Canada's terrestrial radiation monitoring network
2023, Advances in Space Research