Interplanetary disturbances caused by the August 1972 solar flares as observed by Pioneer 9

Journal Article · Wed Sep 01 04:00:00 EDT 1976 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA081i025p04651· OSTI ID:7350898

Dryer, M; Smith, Z K; Steinolfson, R S; Mihalov, J D; Wolfe, J H; Chao, J

Analyses of the dynamical behavior of the interplanetary medium during early August 1972 are carried out with the use of Pioneer 9 plasma and field observations at 0.78 AU. The following studies are discussed: (1) energy and mass estimates for the flares of August 2, 4, and 7 are given; (2) shock wave characteristics are provided; and (3) a numerical simulation of the first two flare-generated disturbances on August 2 as well as of those on August 4 and 7 is demonstrated. The kinetic, magnetic and thermal energy estimates, corrected for potential energy possessed by the ejected mass at the sun, were obtained by integrating over the surface area of a sphere at 0.78 AU, centered at the sun and subtended by 2..pi.. sr. The total energies calculated thereby are as follows: 8.8 x 10/sup 31/ ergs for the first flare on August 2; 4.6 x 10/sup 32/ ergs for the second flare on August 2; 1.1 x 10/sup 32/ ergs for the August 7 flare, which was about 85degree to the west of the spacecraft at that time. The ejected mass was in the range 10/sup 16/--10/sup 17/ from each flare. The energy and mass values for the August 7 flare probably represent lower bounds because of the spacecraft's eastward position relative to the flare's central meridian. As a result, the spacecraft probably sampled a relatively weaker portion of the disturbed solar wind. The assumption of the hemispherical disturbance is supported by the independent observations (>160degree and approximately-greater-than50degree in longitudinal and latitudinal extent, respectively) of the shock-generated disturbance detected in the August 7 case by interplanetary scintillations. The numerical simulation for the first two flares demonstrates the overtaking of the first shock at approximately 1.16 AU by the shock from the second flare on August 2. This shock interaction was also suggested by the observed average shock trajectories. (AIP)

• Research Organization: Space Environment Laboratory, NOAA/ERL, Boulder, Colorado 80302
• OSTI ID: 7350898
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 81:25; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
640107 -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
INTERPLANETARY MAGNETIC FIELDS
INTERPLANETARY SPACE
MAGNETIC FIELDS
PIONEER SPACE PROBES
SHOCK WAVES
SOLAR ACTIVITY
SOLAR FLARES
SOLAR WIND
SPACE
SPACE VEHICLES