Characteristic recovery times of Forbush-type decreases in the cosmic radiation: 1. Observations at earth at different energies

Journal Article · Sat Mar 01 04:00:00 EST 1986 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA091iA03p02851· OSTI ID:5875598

Lockwood, J A; Webber, W R; Jokipii, J R

About 30 Forbush-type decreases occurring from 1972 at 1 AU for which data were available from the IMP spacecraft (P median of approx.1.7 GV) and the Mt. Washington neutron monitor (P median of approx.5 GV) were examined to determine the characteristic recovery times of the events. The characteristic recovery time t/sub 0/ was found to be the same for rigidities of approx.1.7 GV and approx.5.0 GV. Characteristic recovery times for additional Forbush decreases, including some in 1957-1963, were determined, using the Mt. Washington neutron monitor and monitors at cutoff rigidities of approx.12 GV, ans were also found to be the same. Hence the characteristic recovery time of Forbush decreases at 1 AU is independent of energy (or rigidity) over a factor of at least 10. The average recovery time t/sub 0/ at 1 AU is approx.5 days but varies from approx.3 to approx.10 days, and the recovery in most cases is well represented by an exponential. No significant difference in the average recovery time is observed when the solar magnetic field reversed in 1980 nor during the decrease and recovery portion of the solar modulation cycle. A physical model is proposed to explain these results.

• Research Organization: Space Science Center, Physics Department, University of New Hampshire, Durham
• OSTI ID: 5875598
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 91:A3; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640101* -- Astrophysics & Cosmology-- Cosmic Radiation
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC RADIATION
ENERGY LEVELS
FORBUSH DECREASE
INTERPLANETARY MAGNETIC FIELDS
IONIZING RADIATIONS
MAGNETIC FIELD CONFIGURATIONS
MAGNETIC FIELD REVERSAL
MAGNETIC FIELDS
MEASURING INSTRUMENTS
MODULATION
MONITORS
NEUTRON MONITORS
RADIATION MONITORS
RADIATIONS
RECOVERY
SOLAR CYCLE
SPACE VEHICLES
VEHICLES