Dual-frequency radio sounding of the solar corona during the 1995 conjunction of the Ulysses spacecraft
| Autor: | Sami W. Asmar, Mike Bird, T. P. McElrath, Peter Edenhofer, Martin Pätzold |
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| Rok vydání: | 1995 |
| Předmět: |
Physics
Solar conjunction Astrophysics::High Energy Astrophysical Phenomena Equator Ecliptic Coronal hole Astronomy Coronal loop Corona Geophysics Physics::Space Physics Coronal mass ejection Astrophysics::Solar and Stellar Astrophysics General Earth and Planetary Sciences Astrophysics::Earth and Planetary Astrophysics Heliosphere |
| Zdroj: | Geophysical Research Letters. 22:3313-3316 |
| ISSN: | 0094-8276 |
| Popis: | The Ulysses Solar Corona Experiment was performed during the spacecraft's superior solar conjunction from 22 February to 14 March 1995, shortly before perihelion and the transit through the ecliptic plane. The high inclination of the Ulysses orbit resulted in an unusual occultation geometry for coronal radio sounding with the spacecraft's dual-frequency downlink signals. Viewed from Earth, the virtual position of Ulysses on the plane of the sky moved diagonally through the southwest quadrant of the corona from the solar South Pole to the heliographic equator. The impact parameter of the ray path (solar offset) varied from 32 solar radii (R⊙) at the beginning and end of the experiment down to a minimum of 21.4 R⊙ at 45°S. The total electron content of the inner heliosphere, computed from measurements of the dual-frequency ranging propagation delays, is presented as a function of latitude and solar offset. The observations are compared with the coronal structure inferred from synoptic magnetic source surface maps. An increase in electron content by a factor of two is recorded from the center of the southern coronal hole at the pole, to the equator, the northernmost extension of the hole at the time of the observation. A streamer belt, identified by an abrupt rise in electron content, rotated into the radio ray path at southern heliographic latitudes between 16° and 21°. |
| Databáze: | OpenAIRE |
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