Forbush decreases of cosmic rays: Energy dependence of the recovery phase

Abstract

[1] Cause and general shape of Forbush decreases of cosmic rays are relatively well understood, however, the knowledge of their recovery times remains rather poor. Earlier results of theoretical and fragmentary statistical studies are in disagreement whether the recovery time does or does not depend on the energy of cosmic rays. A thorough empirical study of the recovery phase of strong isolated Forbush decreases is presented here, based on the ground based data from the World Neutron Monitor Network since 1964 and three ground based muon telescopes since 1973. In total 39 strong Forbush decreases, suitable for the analysis, have been identified for the period 1964-2006, 24 of them depicting a clear energy dependence of the recovery time and 15 consistent with no energy dependence. All analyzed Forbush decreases with magnitudes exceeding 10% demonstrate an energy dependence of the recovery time, while smaller events can be of either type. No apparent relation between the occurrence of energy dependent/ independent recovery and the IMF polarity has been found. This result provides an observational constraint for more detailed modeling of the propagation of interplanetary transients and their dynamic effects on cosmic ray transport.

Cosmic Ray Induced Ion Production in the Atmosphere

“…The PLANETOCOSMIC code is available at http://cosray.unibe.ch/~laurent/planetocosmics/. Another approach is based on the CORSIKA+FLUKA Monte-Carlo package and has been primarily developed as the Oulu model (Usoskin et al 2004a; and later adopted by other groups (Mishev and Velinov 2007). The two models have recently been the subject of a comparison (Usoskin et al 2008b) in the framework of the COST-724 action (see http://www.cost.esf.org).…”

“…Ions are involved in many atmospheric processes. In particular numerous studies suggest that ionisation due to CR may affect different climate parameters such as cloud cover (Pudovkin and Veretenenko 1995;Svensmark and Friis-Christensen 1997;Feynman and Ruzmaikin 1999;Marsh and Svensmark 2000;Pallé et al 2004;Usoskin et al 2004b;Harrison and Stephenson 2006;, precipitation (Stozhkov et al 1996;Kniveton and Todd 2001;Stozhkov 2003;Kniveton 2004), cyclogenesis in mid-to high-latitude regions (Tinsley et al 1989;Tinsley and Deen 1991;Pudovkin and Veretenenko 1996;Veretenenko and Thejll 2004), atmospheric transparency (Roldugin and Vashenyuk 1994;Veretenenko and Pudovkin 1997;Roldugin and Tinsley 2004), aerosol formation (Shumilov et al 1996;Mironova and Pudovkin 2005;Kazil et al 2006). Some investigations offer possible mechanisms responsible for the observed phenomena, such as the effect of the cosmic ray induced ionisation (CRII) on the global electric circuit (Tinsley and Zhou 2006;Tinsley et al 2007) or ion-induced nucleation (Svensmark et al 2007).…”

Measurements of Forbush decreases at Mars: both by MSL on ground and by MAVEN in orbit

“…It has been found that there is an energy dependence on the FD amplitude (Cane 2000;Lingri et al 2016) and its recovery time (Usoskin et al 2008) due to the energy-dependent modulation of the GCR: the strength of the modulation, the amplitude of the FDs, and the recovery time are anti-correlated with the kinetic energy of the GCR particles. Moreover, due to different velocities and highly complex structures of the ICME encountered, it has been shown that the resulted FDs exhibit a large variation in their amplitudes even for the same energies of GCRs (Belov et al 2015).…”

Study of the Forbush Decreases, Geomagnetic Storms, and Ground-Level Enhancements in Selected Intervals and Their Space Weather Implications

“…However, the intensity and the amplitude of a FD recorded at different locations on Earth are different. The detectors located at different latitudes respond to different median energies of the particles, related to cut-off rigidities (see Usoskin et al, 2008). We selected eight events for which data were available for a number of neutron monitors with a range of median energy E m , and studied the FD amplitude as a function of E m .…”