Tiny solar whirlpools may hold the secret to the sun's blistering corona

science & techPhys.org

Tiny solar whirlpools may hold the secret to the sun's blistering corona

from Phys.org

For the second time in a few weeks, we're writing about research into the temperature gap between the sun's surface and its corona. More and more data from various missions continue to feed this wave of discovery. A new paper by Katariina Nykyri of Embry-Riddle, recently published in The Astrophysical Journal Letters, adds to this growing body of work. She argues that millions of tiny whirlpools scattered across the sun's surface could be the energetic engine driving that temperature difference.

explained

The solar corona is the outermost layer of the Sun's atmosphere. It is a region filled with relatively hot, tenuous plasma that is structured by the solar magnetic field.

The solar corona lies above the photosphere and chromosphere and extends out to the edge of the solar atmosphere where it merges with the solar wind. The chromosphere and corona are separated by a thin, highly dynamic transition region. The outer edge of solar atmosphere where the corona transitions into the solar wind is defined by the Alfvén surface which forms an irregularly shaped boundary around the Sun at heights ranging from about 10 to 20 solar radii (7000000 to 14000000 km) above the photosphere.

Coronal light is typically obscured by diffuse sky radiation and glare from the solar disk, but can be easily seen by the naked eye when the sun is completely or totally blocked in a solar eclipse, or with a specialized coronagraph. Spectroscopic measurements indicate strong ionization in the corona and a plasma temperature in excess of 1000000 kelvins, much hotter than the surface of the Sun.

The solar corona is populated by structures such as prominences, coronal loops, and helmet streamers.

From Wikipedia: Solar corona (CC BY-SA 4.0) ↗ · text CC BY-SA 4.0

so what

Solving it would explain what powers the solar wind and the eruptions that disturb satellites and power grids on Earth. This is one researcher's proposal, not a settled answer.

fun fact

The corona is visible to the naked eye only during a total solar eclipse.

Trump and Netanyahu reportedly clash over whether to resume military action against Iran

the gist

Israeli reports also say the cabinet directed the military to prepare for a possible new attack on Iran.

so what

The United States and Israel have been closely aligned on Iran's nuclear programme and regional threats, so open disagreement between their leaders over military strategy is unusual and closely watched. Whether to resume strikes is a decision with consequences for shipping, oil markets and the wider Middle East.

fun fact

Benjamin Netanyahu has served as Prime Minister of Israel for more years in total than any other person.

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Data: GDELT Project

Illustrative photo · Israel Belkind and Fanny Abramovitch (original) “The Provis…, Public domain, via Wikimedia Commons

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supplementary video · Epimetheus on YouTube ↗

world cultures & travelWikivoyageclassic9th–15th century · Siem Reap, Cambodia

Angkor was the largest pre-industrial city on Earth, covering about 3,000 square kilometres

the gist

Angkor, near Siem Reap in northern Cambodia, was the capital of the Khmer Empire, which ruled much of mainland Southeast Asia between roughly the 9th and 15th centuries. At its height the city spread across about 3,000 square kilometres, making it the largest pre-industrial city on Earth by area. Its growth depended on water: huge reservoirs called barays, along with canals and embankments, stored monsoon rain and carried it to rice fields. That system let farmers harvest more than once a year and fed a very large population through the dry season. The temple complex of Angkor Wat, built in the early 12th century, is the best-known monument and still stands at the heart of the park.

how it works

The Khmer kings built enormous rectangular reservoirs that caught monsoon rain during the wet season. Earthen dykes and canals moved that water into rice paddies, so farmers could grow crops across much of the year. The surplus food supported craftsmen, builders and the workforce that raised the temples.

so what

Angkor shows how a society without industrial machinery could build a city on a scale that rivals modern metropolises, using engineering and water management instead. Some historians link its decline to drought, flooding and shifts in its water systems, which makes it a long-running case study in how cities depend on managing water. The site is a UNESCO World Heritage Site and one of the most important archaeological landscapes in Southeast Asia.

fun fact

The outline of Angkor Wat appears on the national flag of Cambodia.