Nonpotential magnetic fields at sites of gamma ray flares

Technical Report · Fri Jan 01 00:00:00 EST 1988

OSTI ID:6507168

Hagyard, M J; Venkatakrishnan, P; Smith, Jr, J B

The relation between the degree of nonpotentiality of photospheric magnetic fields and the occurrence of gamma ray flares is examined. The parameter delta phi (magnetic shear) and the strength of the magnetic field intensity are used as measures of the degree of nonpotentiality, where delta phi is defined as the angular difference between the observed direction of the transverse component of the photospheric field and the direction of the potential field prescribed by the distribution of measured photospheric flux. An analysis of the great flare of April 24 to 25, 1984 is presented as an example of this technique to quantify the nonpotential characteristics of the pre-flare magnetic field. For this flare, which produced a large gamma ray event, strong shear and high field strengths prevailed over an extended length of the magnetic neutral line where the flare occurred. Moreover, the flare began near the area of strongest measured shear (89 to 90 deg). Four other flaring regions were analyzed; one of these produced a moderate gamma ray event while the other three did not produce detectable gamma rays. For all four regions the flares were located in the area where the field was not nonpotential, regardless of the class of flare. The fields of the gamma ray flares were compared with those associated with the flares without gamma rays, and little distinction was found in the degree of magnetic shear. The major difference is seen in the extent of the sheared field: for gamma ray events, the field is sheared over a longer length of the neutral line.

• Research Organization: National Aeronautics and Space Administration, Huntsville, AL (USA). George C. Marshall Space Flight Center
• OSTI ID: 6507168
• Report Number(s): N-90-26785; NASA-TM-103493; NAS-1.15:103493; TRN: 91-000162
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
SOLAR FLARES
MAGNETIC FIELDS
EXPERIMENTAL DATA
GAMMA RADIATION
MAGNETIC FLUX
PHOTOSPHERE
ATMOSPHERES
DATA
ELECTROMAGNETIC RADIATION
INFORMATION
IONIZING RADIATIONS
NUMERICAL DATA
RADIATIONS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
640104* - Astrophysics & Cosmology- Solar Phenomena