Behavior of the Heliosphere over Prolonged Solar Quiet Periods by
44Ti Measurements in Meteorites
G. Bonino,
G. Cini Castagnoli,
N. Bhandari,
C. Taricco
The heliospheric magnetic field (HMF) is controlled by solar
activity, as established by measurements over the last few decades, but
its characteristics when the sun was quiet for prolonged periods, such
as during Gleissberg or Maunder minima, are not known. Titanium-44,
produced in meteorites, provides a monitor of the galactic cosmic ray
(GCR) flux and allows estimation of the modulation effect of the sun
for the period 1883 to 1992. The titanium-44 activity is consistent
with the expected value, but the increase, due to the last Gleissberg
minimum, is four times greater than expected for a GCR modulation based
solely on sunspot numbers. This result implies that the HMF was weaker
than at present and as a result the GCR flux (for energy greater than 1
gigaelectron volt) was higher between 2.2 to 3.6 protons per square
centimeter per second per 4
steradians at 1 to 3 astronomical units
in solar cycles 12 to 15.
(1) G. Bonino, G. Cini Castagnoli, C. Taricco, Istituto di
Cosmogeofisica, Corso Fiume 4, 10133 Torino, Italy, and Istituto di
Fisica Generale dell'Universita', Via Giuria 1, 10125 Torino, Italy.
N. Bhandari, Physical Research Laboratory, Ahmedabad 380009, India.
