Bishop's Ring
Encyclopedia
A Bishop's Ring is a diffuse brown or bluish halo
observed around the sun. It is typically observed after large volcanic eruptions
. The first recorded observation of a Bishop's Ring was by Rev. S. Bishop of Honolulu, after the Krakatoa
eruption of 1883.
Bishop's Ring was first described after the eruption of the Krakatoa volcano on August 27, 1883. This gigantic explosion threw a vast quantity of dust and volatile gases into the atmosphere. Sulfate aerosols remained in the stratosphere for several years, causing colorful sunrises and sunsets for several years. The first observation of this ring was published in 1883, being described as a “faint halo” around the sun. The first exact description was made by Sereno Bishop who observed the phenomenon on September 5, 1883, in Honolulu; the phenomenon was subsequently named after Bishop. It was the subject of an 1886 professorial dissertation (Habilitationsschrift) by Albert Riggenbach
.
Most observations agree that the inner rim of the ring is whitish or bluish white and that its outside is reddish, brownish or purple. The area enclosed by the ring is significantly brighter than its surroundings. From the sequence of colors with the red on the outside one can conclude that the phenomenon is caused by diffraction
because halos always have their red part on their inside. In average, the radius of the ring is about 28°, but it can vary between 10° and 30°, depending on the dust size. The maximum of 30° is a rather big radius which can only be caused by very small dust particles (0,002 mm) which all have to be of about the same size.
Sulfur compound aerosols derived from volcanic eruptions have been found to be the source for the Bishop’s Ring effect . A Bishop‘s Ring was observed for a long period of time in Japan
after the eruption of Mt. Pinatubo
.
Halo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
observed around the sun. It is typically observed after large volcanic eruptions
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
. The first recorded observation of a Bishop's Ring was by Rev. S. Bishop of Honolulu, after the Krakatoa
Krakatoa
Krakatoa is a volcanic island made of a'a lava in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island , and the volcano as a whole. The island exploded in 1883, killing approximately 40,000 people, although some estimates...
eruption of 1883.
Bishop's Ring was first described after the eruption of the Krakatoa volcano on August 27, 1883. This gigantic explosion threw a vast quantity of dust and volatile gases into the atmosphere. Sulfate aerosols remained in the stratosphere for several years, causing colorful sunrises and sunsets for several years. The first observation of this ring was published in 1883, being described as a “faint halo” around the sun. The first exact description was made by Sereno Bishop who observed the phenomenon on September 5, 1883, in Honolulu; the phenomenon was subsequently named after Bishop. It was the subject of an 1886 professorial dissertation (Habilitationsschrift) by Albert Riggenbach
Albert Riggenbach
Albert Riggenbach was a 19th century meteorologist and co-author of one of the first cloud atlases, the International Cloud Atlas. His doctoral dissertation concerned observations of the first described Bishop's Ring....
.
Most observations agree that the inner rim of the ring is whitish or bluish white and that its outside is reddish, brownish or purple. The area enclosed by the ring is significantly brighter than its surroundings. From the sequence of colors with the red on the outside one can conclude that the phenomenon is caused by diffraction
Diffraction
Diffraction refers to various phenomena which occur when a wave encounters an obstacle. Italian scientist Francesco Maria Grimaldi coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1665...
because halos always have their red part on their inside. In average, the radius of the ring is about 28°, but it can vary between 10° and 30°, depending on the dust size. The maximum of 30° is a rather big radius which can only be caused by very small dust particles (0,002 mm) which all have to be of about the same size.
Sulfur compound aerosols derived from volcanic eruptions have been found to be the source for the Bishop’s Ring effect . A Bishop‘s Ring was observed for a long period of time in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
after the eruption of Mt. Pinatubo
Mount Pinatubo
Mount Pinatubo is an active stratovolcano located on the island of Luzon, near the tripoint of the Philippine provinces of Zambales, Tarlac, and Pampanga. It is located in the Tri-Cabusilan Mountain range separating the west coast of Luzon from the central plains, and is west of the dormant and...
.
External links
- Photograph of a Bishop's Ring, with commentary.
- Meteorology glossary entry for Bishop's Ring.