Coronal-hole detectability on solar-type stars

Technical Report · Tue Jan 01 04:00:00 EST 1985

OSTI ID:6182560

Altrock, R C

It is shown that light from the solar corona, which is integrated over the visible disk (coronal flux or irradiance), can be used to infer the disk passage of large coronal holes. Observations above the limb of Fe XIV 5303 A are used to produce a synoptic intensity map of the solar disk as it would appear in coronal light. The intensity at each point on the map is summed to produce a daily value of coronal irradiance. The time variation of this quantity shows a decrease of 28%, followed by recovery, as a large coronal hole transits the disk from 21 March through 7 April 1984. The occurrence of a coincident geomagnetic disturbance implies that the associated high-speed solar-wind stream strikes the earth. Other solar data sets, specifically sunspot number and 10.7-cm radio flux, do not have unambiguous coronal hole signatures during this period. This technique suggests that coronal holes might be observed on stars, if a suitable method for isolating coronal radiation is used; e.g., radio or EUV.

• Research Organization: Air Force Geophysics Lab., Hanscom AFB, MA (USA)
• OSTI ID: 6182560
• Report Number(s): AD-A-160160/8/XAB; AFGL-TR-85-0232
• Country of Publication: United States
• Language: English

Related Subjects

640102 -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
EQUIPMENT
SOLAR ACTIVITY
SOLAR CORONA
SOLAR EQUIPMENT
SPECTRA
SPECTRALLY SELECTIVE SURFACES
STARSPOTS
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR CORONAE
SUNSPOTS
SURFACES
VARIATIONS
VISIBLE SPECTRA